If need, here are the instructions to solve.
0) Open file .sql of your type of DB (i use mysql and open file mysql_db_struct.sql into jforum-2.1.9\jforum-2.1.9\WEB-INF\config\database)
1) Open panel for admin database. With XAMPP is http://localhost/phpmyadmin/ 2) Create a DB (example jforum)
3) Select DB
4) Into tab SQL copy and execute one query at time of the file mysql_db_struct.sql and build your DB
5) Clear all text into mysql_db_struct.sql and save
6) Open installation forum page, compile form (insert name of DB that you have created and type of DB)
7) Complete installation
8) Work it.
With this istructions, when jforum installation read file for create DB, finish in 0 second because is empty and continue without problem on the DB that you have created.
I hope helped you with my poor english :/
I just found this out. But, for some reason, when we click on the link, it again shows the wizard installation at the top and manual instructions are shown way below (after the footer). You have to scroll way down to find that and it isn't obvious (probably some kind of include tag problem).
And I think the instructions are same as mentioned in the unofficial wiki page.