I just bought one of these little cuties to use ‘on the go’. According to the instructions, the adjustment should be able to be corrected with the upper tension wheel. If you got the book along with the machine, it has pictures to explain

I always start out with a good clean out of the bobbin area, and wind a new bobbin. I might even change the needle if its been in there awhile. I also rethread the whole machine. After a few times of being amazed that there was so much Fuzz in there/ I missed a eyelet threading the machine/ the bobbin thread jumped out of its knotch on the bobbin case...the list goes on. Its a good place to start and a great way to get accquainted with this machine.