Hi Summer,
If you go to your name in the upper right corner of the screen, click on the little down arrow. This is where you find all the profile information you fill in for yourself, including your signature. You can also set all your preferences, and then your signature should appear on your posts.
For multi-quote, just click "multiquote" for every post you want to appear in your response. However, when I tried it this morning, the quotes didn't appear until after I brought up the preview of my response. I am not sure if this is working correctly. I think they are supposed to show up when you are replying - so you can see what you're replying to. Maybe someone more knowledgeable can help with this?
For help, you can go to the bar at the top of the page, and click on "Site Info" and then click on HELP or CONTACT ME. This site works a little differently than some of the other travel sites I am a member of. I am still figuring this all out, too - it's a learning process.
Hopefully, some long time members will chime in.