There are a few different kinds of shotgun actions: break, pump, semi-automatic, lever...
They all load differently. A new shotgun will come with a service manual but most do not have instructions. You need a mentor. Try a local gun club or range. Or ask a competent friend or family member.
Go to a trap/skeet range a take some lessons. You will get advice on what to buy. In the meantime go to youtube and search shotgun shooting. Many videos there.
Get some practice before you buy. And practice often thereafter.
"...from my cold dead hands" Charlton Heston & NRA
"He which hath no stomach to this fight,/ Let him depart." Henry V
Well, there is a manual, and there are videos on youtube like "how to use a Mossberg 500" (not all youtube vids show SAFE operation, IMO). To me, it is the kind of thing you need a trusted mentor to show you how to do SAFELY.
Good luck with the bears; I hear slugs are best for them.