Cant get Guestbook to work on joomla 1.5

[Jaxjoomla]

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in
Warning: array_unshift() [function.array-unshift]: The first argument should be an array in
Warning: Invalid argument supplied for foreach() in

This message i get when i want to create a guestbook. I have visited this link and try to solve the problem, but i find it very unstructured and not so clear. Well i am not so good with phpmyadmin but i tried.

https://www.phoca.cz/documents/3-phoca-g ... -solving70

Use debug mode? then is see this:
500 - An error has occurred.

JDatabaseMySQL::query: 1146 - Table 'discof_db01.jos_phocaguestbook_items' doesn't exist SQL=SELECT a.*, cc.title AS guestbook, u.name AS editor FROM jos_phocaguestbook_items AS a LEFT JOIN jos_phocaguestbook_books AS cc ON cc.id = a.catid LEFT JOIN jos_users AS u ON u.id = a.checked_out ORDER BY catid, a.ordering LIMIT 0, 20

something with install.bak:
I used this file but i was not sure what to do with it.

which prefix i need to use?
Where can i see which prefix i use?

phpmyadmin - Dont know how this exaclty works and make a normal query

Can anybody tell me what to do - step by step
im stressed out.

[Jan]

Hi, you should use prefix, which you have set while installation of Joomla! - you can find some information (step by step) in this forum but don't know your knoledges about sql so no idea if they will be helpful

Jan