Just follow the manual and you should be safe. If you experience problems then contact vBulletin support or post on the forums or something.
Installing vBulletin
To be honest you can rarely trust anyone on the Internet, especially if you are not paying them. Just try it yourself if you have problems then post in the forums and people can help you out.
If you really have no idea what the manual is talking about then maybe you should go for the vBulletin Installation package thingy.