You will need:
A computer - you have that already.
A laser printer or photo copier
Tape - regular "Scotch" tape or packing tape for larger labels
Scissors - if you plan to trim the label close.
Step 1: Make Up Your Label Design
Use your favorite font and make the label any size that will fit under your strp of tape.
If you're using a photo copier you will have to print the page with any printer (ink jet?) then follow the rest of the printer steps using the photo copier.
Print it or photo copy it. You may want to use the external sheet feeder and mark the paper to be sure it goes through the printer the same way next time.
Step 2: Print It Again
it probably actually helps at this point to get a little finger print oil on the tape so the second printing won't stick very tightly.
Run it through the printer again being sure to put the paper into the printer or photocopier the exact same way it went through the first time.
It usually comes out with the second printing slightly misaligned from the first but it should be close enough.
Step 3: Peel and Place
Once it's up, you can trim it further if you like or place it as is.