If your saying that you are trying to install a specific one click install and it isn't liking something that you are typing perhaps you need to be more specific about what is not being accepted where.
For example, the Wordpress one click install there is only one box that accepts free form input. You must select a domain that you have already added under "manage domains" for the first part of the URL, and for the part after the / you can specify with free form input.
If you are still having issues please be specific about which one click you are trying to install, and specifically what you are typing in what box that "it's not liking".
If you are getting past that point, but not able to click a link in the email you are receiving, that's a different issue, you are waiting for DNS propagation to occur, that can take anywhere from a few minutes to 72 hours with the avg wait normally being about 4 hours.