If you go to the control panel for the class where you want the homework portlet to appear, and click on Manage Applets, you should see a link to add the homework portlet.
The list of default class applets is a package parameter and in theory you can add dotlrn_homework to that list and have it be automatically enabled on every new class you create. However, someone else will have to tell you exactly how and where to do this on a package like dotLRN that is mounted multiple times. I have had trouble getting this to work in the past so now when I need to change a package parameter globally I do it in sqlplus, not a process I should be recommending to anyone else. :)
