In order to receive fabulous amount of Runewords and items out from Fortune Crate, you are require to fill up the Summoning Orb to 100% capacity by dissolving Runestones in Tapwar (a match-3 game) .
Refer below links
How to utilise the free Fortune Crates: https://help.monstainfinite.com/hc/en-us/articles/11424078822809
Get to know about Fortune Crate: https://monstainfinite.com/fortune-crate/
Purchase Monthly Pass: https://marketplace.monstainfinite.com/fortune-crate-sales
An account that does not have Fortune Crate bundle or Monthly Pass purchase history are not allowed to tribute from free Fortune Crates.