You will want to find a skateboard that is in somewhat good condition for a more enjoyable ride and smooth transition into your ollie.
Step 2: Find a flat/smooth surface to skate on!
For someone first trying to learn how to ollie I have found it best to be on flat level ground. The less cracks and rocks on this surface the better.
Step 3: Place feet in proper position!
You will want your dominate foot to be on the tail (back) of the skateboard with the other foot just shy of the front screws of the skateboard.
Step 4: Oh the complications!
This next step is the hardest and will come to you easier with the more practice you put into it. It is best not to over think while attempting an ollie this could lead to injury. With your back foot you will want to push down, right when the tail of the skateboard hits the ground you want to jump up in the air slightly and slide your front foot foward.
Step 5: The landing!
Now that you are in the air you just need to place both feet over the board, the best place being right on top of the screws of the skateboard and land balanced