In another thread, "dj" wrote:
Almost anything is "doable" though some things are are more easily and conveniently done than others, and some thing produce better results than others! It's a little difficult to know how to best respond, because you were not clear as to the directory into which your WordPress was installed. You also did not indicate whether you installed WordPress yourself, or whether you used the "DreamHost one-click installer" (or whether you used the "easy" or the "advanced" one-click installer option!)
If your WordPress is installed into a subdirectory of one of your domain directories, then you would approach it one way and if your WordPress is installed in the "base" of one of your domains (directly in the directory from which your domain is served - which is generally one named "youdomainname.tld) then another approach is indicated.
This is because WordPress makes extensive use of apache re-write rules to manipulate urls, which can cause problems for your Joomla! installation if you install it beneath your WordPress installation in the directory tree (in a subdirectory of the directory that holds your WordPress installation). Note that this can be done, but it can be problematic and unnecessarily complicates the installation and maintenance of Joomla!.
Additionally, if you are using the DreamHost "one-click" installer to install these applications, there are further concerns with your directory structure if you want to use the "automagic upgrade" process.
If you post back and tell me how you installed WordPress (whether you did it manually, with the "easy" one-click installer, or the "advanced" one-click installer) and where you installed it (the directory into which you installed WordPress) I'm happy to help you figure out the best way to run both WordPress and Joomla! together on your domain(s).
If you are installing these applications manually you will need to create a database to hold the data, and a MySQL host via which to reach the database, but if you use the "one-click" method that will all be handled for you by the one-click installer. We can talk more about that if/when you post back with the information about your WordPress installation that I asked for earlier.
The term "subdirectory" refers to any directory that is within another (or below, or under, another in the file system structure). Depending upon what directory that subdirectory is in, it may, or may not be accessible to the web. If it is within a directory that is accessible to the web than you can "browse" to it, but if it is not, than you can't.
A "subdomain" refers to a domain that is part of a larger domain, and it can be visited in a browser in the same manner as the larger domain. In fact, the way DreamHost has it set up, you can think of it as a domain of it's own - because it has all the characteristics of any other domain you have installed on DreamHost! Maybe some examples you help here:
To reach a "subdirectory" of your site with a web browser, if your site ( the "larger domain") is at example.com, and you have a subdirectory named "blog" that is "in" the "example.com" directory of your user (ftp/sftp,shell) space, then you would reach it by browsing to "http://example.com/blog/". Now if that subdirectory was outside your "example.com" directory in your user space (say in the same directory that holds your "example.com" and other "domain" directories) then you would not be able to access it directly with a web browser. Sometimes programs store data in such subdirectories so that the program can access the data but a web browser cannot.
To reach a " subdomain" of your site (which you can think of a a "site within a site, or a "sub-site") with a web browser, if your site is at "example.com", and you have a subdomain names "blog", the you would reach it by browsing to "http://blog.example.com".
That said, you can often use a subdirectory for a "site within a site", so that you have, for example, "example.com/blog" and "example.com/joomla", and "example.com/gallery" for you applications (and many do!) and this is no problem at all if your main "example.com" site (directory) does not have an installation installed that does a lot of modifications to the environment via an .htaccess file. If it does, these can generally be worked around, but it can get complicated!
Because of these potential complications, it is often simpler and easier to manage to just put certain application into a subdomain if you have an application in the main domain directory that does this. This is why I really want to know where your WordPress installation "lives" now, so I can besst advise you on how to proceed.
I know that is pretty complicated, but hopefully it will give you some ideas of what is involved. Post back with additional details of your WordPress installation and what you want to do with Joomla, and I'll be happy to try to help you figure out where and how to install it.