How do I connect a gas stove to the gas line?

Turn off gas first.Look at the pipe size serving the stove ,it will be either 1/2" or 3/4" and the pipe on the stove will be 1/2" or 3/4" . Buy a 3/4" x 36" flexable gas line from your local hardware store, buy the kit that will have the fittings and a gas valve with it.The fittings will have threads on the out side and inside, the out side will be 3/4" and the inside will be 1/2".
Install valve at wall pipe using pipe dope on external threads, connect the flex connector to the gas valve, make a loop in the gas flex line and connect to stove using pipe dope .
The loop in the flex line is so that you can slide the stove in and out to connect it.Be sure to tighten all fittings, check with soap bubbles for leaks, Good luck.

You don't give a complete picture, but I'll assume you need to put a pipe tee in an existing gas line and run pipe under floor to where stove will be located, and a 90 degree elbow with a short piece of pipe up through floor near the stove and a shut off valve before the flex run to the stove.

Do not use copper to run gas line!!

This is not that hard to do, but explaining how to do it is like telling you how to ride a bike, I could probably do it in my sleep, but really don't know where to start so you will get the job done right... I wouldn't feel right about helping since I can't see what your'e doing.

Maybe you can find someone near where you live, to point you in the right direction. Most hardware stores have experienced people who can help...

I till smell gas after I hook-up the gas stove

Check to insure you have all the pilots lit and check around pipe fittings with soap bubbles for a leak.