First of all, if you don't already have an Erplain account, you will need to create one! You can do it here. It's easy, and you can get a free trial.
Select your account's icon in the top right corner, then select Edit my profile.
At the bottom of this new page, select Generate new token.
You will then receive a bearer token, set to expire in 2038. Save this token, and then you can start creating queries.
GraphQL (and therefore our API) only uses one endpoint: https://app.erplain.net/public-api/graphql/endpoint.