Arnie, have a look further down this page (at least it is today) for the thread on "Cassette tape to CD" That might help on some background knowledge.
But, if it is simply a Q of connecting a tape to your PC, then it is similar to connecting a tape player to a HI FI. Line out from the tape - line in to the PC soundcard/Hi Fi. If no line out on the tape player, the headphone socket will do nicely.
Conan
PS ANother thought strikes me... If your PC has a radio tuner (many do these days, usually as part of a TV card) then you can either put these tapes onto your hard drive using the above method, or again, if you just want to listen, but do it wirelessly, then search for the Arkon Soundfeeder, which is a great little toy and cheap too. You plug it into the headphone socket of any tape player within about 30 feet and tune the radio to the same frequency (6 to choose from) and voila!