purpose of travel

Dia, you can check either the “tourism” or the “short term visit one”. Of course, if you check both of them, it’s okay, too.
You can ask your friend to issue an invitation letter to you and the invitation letter should show that you will stay with her after your entry. Besides, you just need to prepare your passport and copy of its data page, the completed application form affixed with a passport-sized color photo and the round trip air tickets.