Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
As we all have been patiently waiting for a few weeks now, version 2.0 with the new engine has arrived, along with a plethora of QoL updates:
https://fate-go.us/news/?category=UPDATES&article=%2Fiframe%2F2020%2F0622_gameupdate_notice%2F
For the most part, the loading time has been significantly reduced and the animations are much smoother now (although some have been lengthened).
One thing of important note: while Mash's new skill would give 20% more bond points to party members, because you have to sacrifice 1 slot for her you will end up getting 4% LESS bond points in total. Of course if you have to use her to clear the chapter then it's all good, but in general only do this if you want to farm a specific servant's bond CE, else you are letting bond points go to waste.