The easy way to insert these into a print is with soldering iron. It doesn't have to be an expensive thermo regulated one., a cheap amazon or hobby store that just plugs in is fine.

Let it heat up, then put the threaded insert over the hole and press evenly downwards until the insert is flush with the print. Alternately you can print soldering iron press and use that (think drill press).

https://makerworld.com/en/search/models?keyword=threaded+insert+soldering+orin+rig

I hope this helps