I hate when juiceme me thanks of this kind of questions where someone asks for help.

So first question: do you have CSSU http://wiki.maemo.org/Community_SSU installed? I suggest you install the testing version.

After you have installed that, use it a bit and it will soon (maybe next day) inform updates (I do not know why it takes time). Install updates.

Then you should put the devel repository in your Hildon Application Manager (referred in this forum as HAM) which you will find here http://repository.maemo.org/

After that enabled try installing mobile hotspot. But it seems that many use HEN application to set up wireless.

And are you going to need the N900 as your main phone or just something to play with? There is Maemo Leste if you haven't noticed https://maemo-leste.github.io/. It is not ready yet for phone calls and sms but there has been promised an update soon of some progress.