If you want to add a picture to your profile, the default picture in the top left is a pulldown menu, go to "edit profile." Inside the edit profile page, there is a "profile tools," menu in the top right and it has, "change profile photo." Upload a photo and there you go!
To find people use the channel directory tool in the top right (one small square on top of three small squares), you can turn off the switch that lets you just search for people and content on this server. Hubzilla is a world wide network of similar servers and you can communicate with people across them all. You can find personal channels which are similar to a facebook or google+ page, or channels where there is topical discussions, groups, etc.
Hubzilla is much more than just a social media platform, but it does that quite well and it is a good place to get started!
See you around, make sure to connect with me.