FAQ101, "How do I join a community and read its entries on my Friends page?" has been updated with text explaining how to accept an invite. It's now in the fourth paragraph.
This information was more appropriate in each of these FAQs rather than creating a new FAQ, so I added it in. Since I wrote up my own text and added it in, I'd appreciate it if other eyes could read over it to catch anything I missed.
acerbic, love me. :)