You don't have to do much, really. Just make sure you have designated a folder(s) to share from and keep it stocked with files people want.

On Limewire, you designate folders thru Tools>Options>Sharing. Click the ADD button, and browse to the folder you want to share from. It should be much the same for BearShare, but I don't run it anymore, so I can't remember the menu system
You should also remember to NOT rename files you have downloaded, and to properly name any new files that you add to the network, so people can find and download them easier. You can get naming hints by reading how others have named theirs.

Have a Blast