Re: new and having problems
Welcome to the forum from an old Florida native.
Chain alignment and tension is critical. So is the rear sprocket installation. The rear sprocket must be concentric to the rear hub with absolutely no wobble. The chain tensioner is either required or not depending on your frame. Tension is very important. 1/2 to 3/4" slack on the upper portion of the chain, no more, no less.
Some folks have had problems with rough teeth on the rear sprocket which can be smoothed with a metal finishing pad chucked up in a drill or a side grinder, if you have one. Check your alignment carefully and spin the rear wheel to check for sprocket concentricity to the hub.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"