How do I go about borrowing off my 401k is that I would go through the employer or is there a number that I can call

You would contact the company or person who is the administer for the plan, this may be your workplace, but is normally some investment company. This info should be provided in your 401K info packet you received or contact info on the statements you receive from them.

If you can't find it any where else your HR dept where you work should have that info