How to add a new archetype
 

I found a home brew primal path that i really like and was wondering how i may be able to add it into HL

The easiest way to figure this out is to have a look at the existing archetypes. Study that to learn what you need to do. This is one of the more advanced things you can do within the editor though so I would recommend starting with a spell, equipment, a monster, etc. These will get you familiar with the Editor so you better understand what needs to be done.

That's a loaded question, the answer depends on how much experience you have with the editor really.

If you have limited experience with the editor and scripting I would first hit up this post from Mathias on the Pathfinder forums. Most of what his links talk about apply to all of the editor and HL, not just to Pathfinder although you'll find that 5e will have some differences.

I would then head over to the github wiki and look at some of the code examples and knowledge that other people that have worked on the community files are sharing.

And finally this link is to the official authoring wiki, but save that for the hard scripting questions that will pop up later.

For classes specifically, you'll be in a smaller section of the editor. There is a main tab for Class. You define subclasses/archetypes on the Custom Ability subtab under that section.

If you go in the editor and navigate to that Custom Ability tab, you can do a New (Copy) and copy an existing archetype for the same class as a starting point. If it's not a Totem Warrior type archetype, I would suggest copying Path of the Zealot from the community files. The Totem Warrior barbarian path is an advanced creation, requiring knowing how to set up a new Tab (called a configurable), which isn't the easiest to learn.