Also, if that is the first tin of pellets, just keep shooting until they are gone to aid in breaking the riflei. 500 to 1000 shots for break in if you can.
Then clean the barrel, fire five shots with the pellet you are testing, and then shoot for group.
Clean the barrel and fire five of the new test pellet before shooting for groups.
Look up the artillery hold and then experiment with your rifle. I grab the sling at the front with the stock resting on the top of my hand with my fingers wrapped around the sling. In the back, i don't use the thumb hole for my thumb, but instead hold my thumb straight up the side of the stock.
I replaced the trigger with a much better replacement.
Having said all of that, i still never found a pellet the rifle would shoot well until recently. The Umarex Ruger Superpoints shoot pretty good out to at least thirty yards, I was betting my grandson on whether or not i could hit the last pellet hole not too long back, and i am still using the scope that came with it. Several of the heavy choices shoot well also, but they hit too law to adjust the scope without shimming.
You can also try seating the pellets you are using, but in my rifle seating them reduced accuracy.
Good luck!