You already shot an inline so you need all the same equipment. A the minimum:
- bullet starter
- volume powder measure
- FF black powder
- percussion caps
- projectiles
- cleaning equipment, soap&warm water (I like CLP after)
- lube
I highly recommend a range rod. That is a sturdy steel sectional rod. Assorted jags for loading, cleaning and patch removal. Patches for cleaning and shooting. If you plan to hunt some tubes with measured (or weighed on scale) charges.
I have not used sabots in a sidelock. But you can. I think that is a little pricey and not as old fashioned gratifying, Swaged round balls maybe a reasonable fun load to shoot. I would start with round balls and prelubed patches. The round balls might work best at lighter loads. I have been casting Lee REAL bullet mold in pure lead. That works well. You can buy cast bullets. No patch is used. The Lyman Great Planes mold is highly recommended on this forum. If casting that might call for another post. Or buy a furnace and read the instruction that come with it.
Edit: You will want to determine the rate of twist when deciding where to begin with bullets or balls. The balls can be pushed harder with a slow twist but more important the heavy bullets NEED enough (faster) twist to stabilize. Too much for one post.
Now that I think about it, the Thompson Center owners manual, available on line, will have all you need to get started.
I never shot a 1" group at 100 yards with any gun using simple open sights. So; dont be disappointed. My first shots with a new gun are 25 yard sanity shots. Then out to 50 where I like to be a few inches high. I generally do all my shooting at 50 and then fire a few at 100 to see where I hit and verify nothing went weird on me. Some people wipe down between shots as do some inline shooters.
De grease the barrel before your first shot and fire a couple caps. Per the manual. Maybe check out youtube for some how-to.
They key for a hunter is to get off the bench and practice some field position shooting.
The cleaning takes a lot longer than an inline, but the inline breech plug is a big hassle and you got none of that to deal with. I have a nipple wrench and remove my nipple before and after every range session or day out hunting. You know, you remove the barrel for cleaning, right?