We only offer instructions for MailChimp using the MailChimp Widget and the Genesis eNews Extended widget.
If you look in the WordPress repository, the Aweber plugin gets terrible reviews and has not been updated in over a year - that's why we have not installed it.
You can install Aweber forms manually using a Raw HTML Snippet.
Here are instructions from Aweber on how to get the form code...
Once you have the code, you can use a Raw HTML Snippet to add the code to your blog.
(You can also send us the form code and we can add it to your site for you - but you'll have to get the code from your Aweber account)