>>1126709It's good that you ruled out climbing up it, or the ladder. Ladder + Chainsaw is a definite fucking no.
If you've never cut down a tree before then sure, a bow saw is going to be easier. Draw the wedge on to the tree before hand, cut out a wedge 1/3 the diameter of the tree into the direction you want it to fall. Once the wedge is out, stick a square ruler or something T shaped into the wedge to see how close you got.
Don't go up the tree unless you have to. If you don't know how to fall a tree, you should not be climbing one with a chainsaw. Just take it slow, make your cuts right, and make the back-cut level for the whole duration of the cut. If you're doing it with a bow-saw, it will get pinched, so you will 100% need a wedge/axe head to prop the cut open so you can continue cutting. Otherwise you're going to look like a right idiot.
A chainsaw will get pinched too, but they have a bit of leeway with a tree that small.