Installing openwrt on GLiNet Mifi

Let me preface this with who I am and my goals:

  1. I'm a complete networking newbie with only limited python knowledge
  2. I also have a shadowsocksR VPS
  3. I want my GL-Mifi to auto connect to my VPS

I don't really know what I'm doing. I do know that I have to install ar71xx of 18.06.4 using LuCi interface with an upgrade link. I'll try it out tonight, but I'm just poking in the dark at this point. I'm not sure how to SSH into my router if it's not connected to the internet. I wish somebody could give me some pointers or some general steps to get to where I am now (brand new GL Mifi) to where I want to be at (router now connects to my VPS).

Don't have to do everything for me, as long as there is something for me to read, I'll try my best to learn along the way. I just need to know if I'm going in the right direction.

Thanks in advance!