Installing Brass Threaded insert into chassis

[Gee]

What the best way to install threaded insert like these into plastic chassis parts?

http://www.tonysscrews.com/category....?categoryId=12

Should the hole be small enough you need a hammer to get them in or loose so they just slip in with the press of a thumb? Heat them up so they plastic melts around them?

Should they be set in with epoxy?

The split down the middle of them make it look like they should spread open when a screw is installed. I haven't installed them before so I am unsure what the best way.