Although your incubator doesn't have a label that I can see, it looks just like mine, only dirty!
Do an online search for the GQF manufacturing site, click the "Instructions" tab at the top of the page, and down at the very bottom of the list you will find instructions for your kind of incubator:
(Hova-Bator thermal air incubator 1602N and 1582N)
Although there are much better quality thermometers around, if you aren't feeling like investing a lot in the incubator at this point, you could start with a dual measurment temp& humidity gadget that you can find at places like
Walmart; its Accurite brand. I have successfully hatched chicks with one of those, but I -do- think it was 1* inaccurate in it's temp measurements.
Although still air incubators need higher temps than ones that contain a fan, I found that 100F was a good temp for the one I have similar to yours, though some people say 101F is the way to go.
The wafer (circle) inside the lid is part of the thermostat. The little metal handle on the outside is the temperature adjuster. Start by simply plugging it in. After 24 hours, see what temp it is, and turn the metal knob to increase or decrease the temp., letting it have time to adjust. Then adjust it again until you get it to the temp. you want. After you adjust it, if you store it at that setting, it should still be very close to the correct temperature if you need to plug it in to rescue a clutch of eggs from a suddenly non-broody hen.
On mine, 1 complete turn of the metal handle is 4*F temp. difference. Counter clockwise (if you look down from above) increases the temp, and Clockwise decreases it.
Hope you can get it up and running alright.