For this you need the bike to be on the center stand, or balanced upright. Testing on the side stand will not result in an accurate reading.
Otherwise, all you need is a paper towel or rag to wipe the dipstick with. Once the bike is upright, unscrew the dipstick (on the left hand side of the engine, in front of the gearshift lever), remove it and wipe it off:

What we will be looking for is where the oil level sits on the crosshatched section. Now, rest the dipstick back in it’s hole but do not screw it back in:

Leave it for a few seconds, then remove it without dragging the tip against the edge as you do so. Now, look at the oil level:

This particular bike has just had it’s oil changed with the correct amount and as such the level is 3/4 of the way up the cross-hatched area. We generally like to keep them between 1/2 and 3/4 of the way full – any lower add oil.