I have family up in Louisville, my cousin's dad is a professor at Bellarmine. The drive seems pretty simple judging from Google Maps (making sure I don't tell you wrong info, I'm turning 18 on Friday and don't know my roads well yet). All you'd have to do is go I-65 to Nashville, and once in Nashville go I-40 towards Knoxville. It will be a pretty boring drive of nothing once you get on I-40, you will pass through a small city called Lebanon and the river is about 20-30 minutes past that. You will pass over the river 4 times while driving on I-40, and you'll get off at exit 268. Since you're coming from Nashville, the general route to the river is to take a right and head up to the area around the dam or at Happy Hollow.
To get to Happy Hollow, you take a right from exit 268 and start driving and it will come up on your right after a mile or two. HH is 5 miles downstream of the dam. To get access to the dam all you do is keep going straight instead of getting off at the Happy Hollow turnoff. You will come up to an intersection with a gas station/mini mart on your right, you'll want to turn right at that intersection and the pull off for the dam isn't even half a mile up that road.
To tell you specifically, here is a helpful link.