Just joined a league today and was wondering how coach hiring is done. Is it possible to Fire coaches currently on Staff? How do you hire new coaches? I realize it has be a promotion from their current position but how is it done exactly?

Let's say you want to fire your head coach. There are two ways to do this: 1) Promote a coordinator or position coach or 2) Hire an unemployed coach. If you do either of those things, your coach will automatically be fired.

When is the time frame to hire/fire? Anytime during the year? Currently we are in round 1 of the 2020 draft. Is it possible to hire an promote a secondary coach from another team to be my OC and how is that done?

You can't directly fire a coach, but you can replace a coach by signing a new one for their position. Coaches can only be hired from a different team during Free Agency (before the draft). Coaches can not be signed from another team during late free agency.

You can hire coaches during any stage except during the draft (you can queue up your offers but they won't be considered until the first free agency stage after the draft). Outside of that restriction you are free to replace any of your coaches at any time.