Your machine looks similar to my mom's old Singer that I learned to sew on. For the tension problem you showed, I agree with the first reply - turn the tension knob clockwise to fix that. For reference, in your picture the tension was set at 0-1; normal is between 3 and 7. I would turn it up 1 number at a time, until the stitches are locking inside the fabric.
When I get skipped stitches, it's usually because of a dull needle, or because I haven't dusted out the fluff from the bobbin area recently. I've found that defluffing thoroughly and regularly is the best way to keep my machine working well.
Just in case you haven't found a manual, that dial on top (Norm/High/Darn) will adjust the foot pressure. Norm will work for most things, but High can be helpful if you're sewing heavy fabric, and Darn will have low pressure - useful for darning, or working with fine and/or slippery fabrics. I wouldn't change it most of the time, but the one time I've found it useful is when I was sewing light fabric and it was gathering/puckering. Switching to low pressure (darn) fixed it.
Another tip if you're getting funny stitch tension issues is to snip off your top thread near the spool, pull out the snipped section through the needle (so that you're never pulling thread backwards through the tension knob), and then rethread it. This often fixed my problems. With new machines it's important to thread the machine with the presser foot up; I don't know if that's true of older ones, but it can't hurt.