You asked how to leave messages for people. When you're looking at someone's profile page, for example "Grinning Cat's Page" for mine, you can leave them a private message using "Send a Message" on the left, under their picture. (If you're not already "friends" with them on the site, it'll let you send a friend request instead, where you can include a short message. The site sometimes gives you links to send a message in other places where your friends' names show up.)
You also asked how to change how your name appears here. After choosing "Settings" (upper right, below "Sign Out", "Inbox", "Alerts", and "Friends"), "Profile" (upper left) lets you change your displayed "Full Name", as well as add or edit a photo if you like. Just as important for folks who are not completely out, "My Page" lets you change the "Address" of your profile page (for example http://atheistnexus.org/profile/GrinningCat -- and I could choose something else for the "GrinningCat" part). Search engines like Google can find that address, so the choice there matters.
Thank you for the invitation to be your friend, Naomi. I look forward to getting to know you. There are many topics from which to choose and you will quickly learn which ones you want to follow and the individuals with whom you share interests.
Joan, I used "Character Map" (on my U.S. Windows computer), double-clicking on each letter I wanted, then clicking the Copy button, then pasting it into here. The exclamation point should really be on the left (at the end) of the phrase, as part of the Hebrew, but I didn't know how to indicate that. Sometimes for non-English letters, I'll copy-and-paste from Google Translate or some such. (When I'm not certain of the translation, I'll often translate it in the other direction as a rough sanity check. Reminds me of the story of an early computer translation experiment, where "The spirit is willing, but the flesh is weak" translated from English to Russian and back to English came back as "The vodka is strong, but the meat is rotten.")
Naomi, I completely agree with Joan's assessment of this community! We certainly exemplify the fact that there's no atheist "chief rabbi" or "pope" -- no matter how much fiery certainty some famous atheists and skeptics bring to their opinions. And we do treat each other with respect and kindness, as fellow human beings behind the screen names.
(By the way, your "Website Address" on here doesn't have to be your street address. It's up to you how much information you reveal. Anyone, member or not, can see profiles -- and most pages -- on Atheist Nexus. To anyone add "anything", including Google and other search engines. You can edit your profile information using "Settings" in the upper right, underneath your name.)
Grinning Cat, I am impressed, you spelled outside of the English alphabet!
Naomi, we are a skeptical bunch of people exploring alternative options. Questions, doubts, fears, and confusions pop up from time-to-time, always treated with respect and compassion. I like the safety I find here
Welcome! ברוכה הבאה! (Talk about theism sometimes being baked into the language...)
You'll find lots of groups and forums here. Unlike some sites, joining groups doesn't clutter your "home page" or "timeline"; some people are members of many dozens. I particularly enjoy the relaxed "Hang With Friends", and (guessing from your name) you might also be interested in "Jewish Atheists".
And I keep discovering interesting things through the "Latest Activity" list on the bottom right. (You may need to scroll down to see it.)