Work with other data tables

Maybe stupid question but, how can I work from a scenario with other data tables?

It’s easy, but may seems not obvious.
You can manipulate data from other structures (tables) using links on them. These links are IDs of objects in type of Link fields. (check this tutorial out).
If you need to find objects and then manipulate them, use the ‘Find objects’ step. It’ll help to find the objects from other structures and save their IDs in the field of current object.