I am also new to air guns, "8 Months". I had the same question when I first started. What I found out was basicaly on my own as you will probably do also.
I start at 10 yards to get it on the money. Then I move it out to 20 yards and re-adjust.. Then I move it out to 40 yards and re adust again.. I only have a couple rifles that I shoot beyond 40 yards..
You will notice that after you adjust your scope to 40 yards and are grouping where you want and then go back to 20 yards, and 10 yards you will be I think to high...

Try it and you wil see.. I am lucky in a since that I have a few air rifles and I have one set dead on at 20 yards and the others at around 40 yards out.
This is not that complicated. After you adjust your scope to shoot at 40 yards and back to 20 yards try and find the bullseye on the target and manually adjust with rifle up or down to find out if you need to aim lower or higher to hit the bulls eye. Thats how I did it before I bought a few more rifles.
This procedure of adjusting manually works fine for me. If you have an Objective adjustment then you will have to adjust it for distance first.
Just think of having iron sights. You always have to make you wind and distance adjustment manually by placint the sights either up, down, right or left a bit to hit your target.
I am bad at explaining things and this probably is not the proper proceedure but it works for me...

Some of the other experienced scope hunters will probably heip you out more..
Good Luck
Gene