Google found:

https://www.youtube.com/watch?v=jDL5q6THrtA

https://www.youtube.com/watch?v=AzwSjpi5aQ0

https://www.youtube.com/watch?v=_MjTbz98NOc

Presentation Lecture 13-Indexing SAED patterns

some notes in addition. The videos provided by Stefan Baunack mainly provide basis for indexing of electron diffraction patterns from polycrystalline material, whereas the lecture notes are more general. There is tons of material like these in the internet. I always state the necessity of fundamental understanding of the diffraction process, for SAED in the context of the special situation in the TEM with short wavelength, often providing a more or less undistorted 2d part of the reciprocal lattice containing its origin.

Generally, the process of assigning hkl indices to the spots (rings) is referred to as indexing. What you then do is deriving a structure model (complete crystal structure or at leeast a translation lattice) for the material under investigation. That either occurs by known candiate structure models (e.g. in view of chemical composition) or by carefully deriving a structure itself.

It is really quite complex to determine the space group of a crystal. Once that is known, the Weiss Zone Law can be used to determine the zone axis (viewign direction) and there are clear rules how to work out the lattice spacings for each type of crystal class. Be aware that often the camera length in SAED is not calibrated to the precision that would be required (