How to use viewblock api 

Hi, @balthazar @team
How are you?
I'm going to get Data stored of Arweave like as https://viewblock.io/arweave/stat/cumulativeWeaveSize, so that wanna add Arweave key metrics to our site; https://depin.ninja.
So I tried to access api.viewblock.io/graphql, but I can't get find where I should get API_KEY and query docs.
Would you please help me to get relevant api and api documentation?
Thanks.