What machine do you have?
Tension will dependant on thread, material being sewn, and your machine. Sometimes you gotta sacrifice some material in "testing". Then attack your project. If you find the settings and speeds that work for you, write them down for future reference.
Depending on your machine, adjustment may not be available. Typically there is a knob directly above the foot/needle bar, on top of the machine.
"J" in this image.