When you purchased you should have seen a little How to sideload guide but if not we can make a public copy and link it to you ? We haven't tested at 90 HZ but i don't see a reason it shouldn't run at that high of a refresh rate ?!
Here's a copy of the Sideload Guide : https://docs.google.com/document/d/1mYv6_bnZTG0cwYU7ULXd94FYpEjYYkusEaYk3JEnAcQ/...
Please let us know if you have any further questions !!!