If you want to learn more about flintknapping read my post on Flintknapping Arrowheads made of Flint, Glass and Obsidian. If you are looking for How to Fletch an Arrow watch the video on Project Gridless' YouTube Channel.
Hafting is all about attaching a finished arrowhead to an arrow shaft.
Here is a simple 3-step breakdown of the process.
Notch the arrow shaft a size that is close to the arrowhead you are attempting to haft.
Use pitch (or a similar material) as a glue inside the notch to help affix the arrowhead to the shaft.
Using soft deer sinew (or a similar material) wrap around the shaft, the notches in the arrowhead both horizontally and diagonally. (To soften deer sinew, chew or suck on it in your mouth for several minutes until you feel they are soft.) After you are done the deer sinew with harden and tighten up, holding the arrowhead in place.
Below is several videos which demonstrate various ways of how to haft an arrowhead.