Here  I am going to do a lot of pictures, I have found for beginners it is easier to look at pictures and follow along . 

I did this tutorial in psp 9 but you can do this in any version of psp.

So here is where we start we go to File and go to Blank image and type in 250 x 100 that is the size tag I am making you can change the numbers to anything to make a tag.