Hi fiddleman, welcome to the HP Forums. There are lots of 'how to' documents out there, showing you how to transfer cassette tapes to your computer. You can use those documents to show you the ways to connect a tape player to your computer, to play them.
Here is an example of one document showing you how: How to Transfer Cassette Tape to Computer. I have never done this before, even though I was alive for the 8-track revolution. Good luck :)