I read the article on the Wiki but how do I access this Shell to add cron jobs?
Firstly, you need to enable Shell access for the user you wish to log-in with, you can do this in the panel by going to Users -> Manage Users, then clicking Edit for the particular user. You will then need an SSH client to actually log-in to the Shell and issue commands. The client you use will depend on the operating system you use, I use PuTTY under Windows.
More information can be found in the wiki article linked below;
Save [color=#CC0000]$50[/color] on DreamHost plans using [color=#CC0000]PRICESLASH[/color] promo code (Click for DreamHost promo code details)