Ellen, looks like you already found your way around, but anyway welcome to Atheist Nexus!
Nexus has many ways for members to be involved, make friends, learn, and express yourself. The welcome center is composed of Nexus volunteers, sort of like greeters at your favorite store.
Get to know people with similar interests by searching on Groups. Use the search box on the Groups page, or browse through the many pages of groups, to see what's there. There are Nexus groups for many states, cities, countries, personal expression, hobbies, and many other groups. Get to know people based on what you enjoy, or what you have in common with others.
To find local atheist groups and make friends or chat, check out Meetup.com. (note, Meetup is not connected to AN). Join Meetup and search on a key word, such as atheist, skeptic, freethought, to find a group.
Support Nexus by visiting Amazon.com through Nexus (see the Amazon box on the right). Buying from Amazon via the Nexus site does not increase your cost, but results in a small donation going to Nexus.
Terms of service helps you know the "rules". You can also find the TOS on the bottom right of the main screen.
The right sidebar shows recent posting activities and discussions by Nexus members. Click on "more" at the bottom for additional activities.
If you have general questions about Nexus, how to find what you want, or other questions, feel free to ask me or another volunteer member of the Welcome center!