Setting a binocular dioptre (right eye setting) is very easy to do, and takes less than 10 seconds with practice.
So why do binoculars have a right eye dioptre wheel ?. Not every ones eyes are exactly the same. So one lens on the binoculars needs to be adjusted to compensate.
Firstly either close your right eye, or place the objective lens cover on the right side. Focus as normal on a mid distance objective around 30-50 metres away. Then repeat with the other eye by closing your left eye or covering the left hand side objective lens. But this time , instead of focusing as normal, use the right eye adjustment wheel. You will see this near the right side eyepiece.
Be sure when you are focusing with both methods above, you are focusing on the same object each time. Once you have done this, the binoculars should be set for you.
Note that some zoom binoculars will have the dioptre adjustment on the left hand side.
Once set, you should see small increments next to the dioptre wheel. This is so you can remember your mark, in case some else borrows the binoculars and moves it from your setting.