Assalamu Alaikum (try to implement this greeting more often since this is the greeting of Muslims to one another)
The mosque is compromised of two sections, one for women and one for men. Sometimes they are each on different floors or even in separate rooms. And if they are in the same room, the women are praying behind the men.
You should dress modestly, covering your head and body (hijab and abayah). If you do not have a abaya yet, then try to wear a long skirt and a long sleeved, long shirt. Otherwise wear loose-fitted clothing which cover your body in the same manner.
If you plan on praying there, then you will need to perform wudhu (ablution). You can do that before you go to the mosque but you must maintain it til you finish prayers (ie, no passing gas, or using the restroom), or at the mosque before prayers. Then after that you will offer your prayers with the women. Prayers are done in rows so you will follow what everyone else is doing
I'm sure your friend will show you when you arrive.
