To start with as long as the sensir wont melt, it doesnt matter where its located, fit it, and lower the z axis until it triggers, then measure the distance from nozzle to bed, if the nozzle is above the bed then you need a negative number, i never measure to be fair i make a rough guess and fine tune from there, its not the best way but it works
You will need to go and edit the firmware and turn on mesh levelling (bi linear in marlin), i used a 4x4 grid and thats working for me,
Before editing the firmware you need to go into the printer menus and write down all the settings, steps per mm, acceleration etc so you can pop these into the new firmware
What brand of printer is this, i have a ctc i3 pro b, if its one of these i can email a copy of mine and you can edit from there is you want,
Its not a quick and easy thing to do, but ask away if you get lost or stuck

OK. I saw a video that said to basically move the sensor around till you get the right height? That is a serious pain. I tried it:/ I did however manage to get my PC connected to my printer and am looking at instruction vids and posts on how to set it up. The firmware changes don't seem too scary but I still have the question I started with. After you get the sensor to trigger and then measure the height of the nozzle. With or without the PC how do you adjust the nozzle to the correct height to achieve good prints? Is it in the firmware and if so where is it? LOL So strange. I really thought it would be just a quick offset correction and bang!! But, not so I guess. I have not had much time to tinker but am going to really give it a go in the next week. It is unfortunate that I made more prints with thing in the first three days then I have in the last three weeks after I put the auto leveling thing on LOL. It really is just sadistic fun but bummer cause I have a lot of stuff I wan to print and can't
Anyways thank you so much for your help and I hope I can get her rolling soon. It's a LESHP self assy printer I got off of Amazon. I did a ton of research before I bought it and knew what I was getting into so I am patient. Thanks again

Ok so I am having another issue. I started to set up Marlin to get the bed leveling to work but having problems getting Arduino to accept the changes to the firmware. I didn't do anything crazy just changed a few things according to videos and posts I have read. Every time I try and verify it say's that the board does not recognize the pin assignments? :/ All I did was change like the feed rate etc. I did not try and verify it before I started but like I say I didn't change much. Any ideas?