Next steps?

Hey everyone,

Machine: Mid 2012 Mac Pro 5,1 3.33 Ghz 6-Core Intel Xeon 32 GB 1333 Mhz DDR3 ATI Radeon HD 5770

Had a hard drive failure and was having issues getting an OS on it. Ended up getting Open Core Legacy Patcher Big Sur.

I have a Radeon RX580 I used to have in it that I want to put back in it.

I also have a dual tray, 2x X5690, and 96GB of Ram coming.

What should my next steps be for upgrading the OS? Are there videos I could watch? Is there an order I should do it in? Just wait until I have the new stuff and do it then?

Thanks for any and all help!