It suppose to mean:
Do you want to know my (girl) friend.
Quieres = do you want
ser = to know
amiga = to normal girlfriend (not necessary dating).
About dating:
girl friend = novia
boy friend = novio
novia and novio can also mean husband or fiance.
If you have other Spanish problems, you can go to:
www.wordreference.com
It is a online dictionary and it is really helpful.