In reply to:
Will i just have to make another mysql database?
Well, you have to do another installation, but whether you make another database or not is really up to you, as WordPress let's you set a "prefix" for the tables so that multiple installations can share the same database.
Since DreamHost lets you have as many databases as you want, however, there is little reason to do this unless you want to be able to back up all the data for multiple sites in one MySQL backup (or course, the "all your eggs in one basket caveat applies here is one argument *against* that, though it might be convenient).
As for me, having numerous backups/dumps floating around (that are *supposedly* managed in an organized manner), I like using a descriptive table prefix to help indicate which site the data goes with even if I am using a separate database (but I realize that is a bit anal!)
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--rlparker