Just stick them in the enclosure, plug it into your comp, and turn it on. Your computer will recognize the mass storage device, install drivers, yadda yadda yadda. Then go into computer management, go to disk management, and then you should see the HDD right there. Assign it a drive letter if you want, and then format it however you want. Same as every other drive.
First look at your computer and see what port (bus) that your computer offers:
I will list it in order of speed:
USB2.0 Slow and relative easy to use
1394a - faster than USB but more cost
1394b - faster then 1394a and cost even more
eSATA - king of the speed 3.0Gb can configre RAID with multiple drives