How i can make a test site ?

[DeanLag]

Copy paste your current folder into another folder.
For example, if your forums is www.domain.com/forums; copy it to www.domain.com/test
Create a new database in your Control Panel so that if you make any database changes, it won't affect your current database.

Also make sure your test site is password protected as it shouldn't be accessed by the general public. And no, you don't need a new licence for that.