I would first try to go to https://support.ca.com and log in using your same credentials you use of Communities.
If you are logged in now, it should automatically use your cached credentials.
Once you get to the support page, hover your mouse over the Download Center arrow and choose "Download Products".
After you're redirected, type in "CA Application Performance Management - MULTIPLATFORM" and choose your APM Release, Gen level, then search.
If after all that you still do not see the software, you will need to contact CustomerCare and let them know your fulfillment is missing software.