For checking the bobbin tension search you tube for Jamie Wallen. He has a good methiod fkr checking your bobbin tension. I have had a Sweet 16, which is the same machine virtually, and have never had to adjust my bobbin tension.
Foe the top tension: that needs to be adjusted with every new thread. You have to really crank that top disl. It is not like your regular machine. .Crank the dial one full turn and check your tension. Do it again. Move the dial until it looks good.
Try rethreading the machine. Make sure the needle has not come loose.
The Handiquilter site has tons of information.
Also join the Yahoo group for HQ Sit Down machines. Don't have the exact name but you should be able to search the groups for it. Just tons of info and help there.
These machines are great but there is a learning curve. Keep going - you will bond with your machine and have happy times.