OK, as requested.
For the purposes of this effort, the simplest option (short of full-on digital surround sound etc.) is a mini hifi.
You logically need to think about the connection between the different devices (ie, your TV and your sound system). While other options exist, if you're just after something basic, RCA will suffice (
http://en.wikipedia.org/wiki/RCA_connector)
Step 1: Go to your existing TV, and see if there are sockets like these (we're interested in the top ones - red, yellow and white):
Make sure that there are words along the lines of "out" or "output" or something similar near them.
Step 2: Go to your local electronics store (in Australia, Dick Smith Electronics, Harvey Norman, Retravision, Good Guys, are ideal; I think that Best Buy would be a similar US equivalent, although I've obviously never been to one).
Step 3: Ask staff for a mini or micro hifi system that has RCA inputs
Step 4: Select a suitable system. You should be able to do this for between $50 and $500.
Step 5: Buy RCA cables. They look like this:
Step 6: Give it to Grandfather as a gift
Step 7: Plug speakers into electricity; plug rca cables into TV and speakers
Step 8: Set hifi system to "aux input" (or equivalent)
Step 9: Turn TV on
Step 10: Adjust volume on speakers
Step 11: ????????????
Step 12: Profit