How to setup time machine to work on home network?

I have searched these forums and apples sites but can't find the answer. I have an external disk drive attached to one of my macs on my home network. When I try to setup time machine on my laptop (macbook pro) it does not see this disk. What network settings to I need to have set so I can see this drive?

All of my macs are on leopard. When I start the time machine setup with the mac that has the connected disk it sees the disk fine. So I must not have all my network/sharing settings correct. I do see the mac as a shared in finder.

Thanks for any help!

 

I probably don't understand this....

"Time Machine can also back up to another Mac running Leopard with Personal File Sharing, Leopard Server, or Xsan storage devices."

This is from apples web site. How do I setup personal file sharing or leopard server? Would this allow me to backup to an attached drive?

 

ibook4a: I got this to work by following your method of using finder. After doing this it just popped up in TM.

I also had to reformat my disk to be "Mac OS Extended (journaled). Just letting others know in case they are trying to do the same thing.