Pro tip when using flows: the standard "Lookup Record", "Update Record", and "Fast Lookup" blocks effectively contain a SOQL query apiece. This means that if you ever find yourself in a situation where you need this flow to be triggered a bunch of times in a single transaction--such as an "On Create" process builder trigger and you're doing a bulk upload--you're going to hit your governor limit of 101 SOQL queries very quickly (if you have one Lookup and one Update block in a flow, you'll hit the query limit on your 51st record, for example). Heaven help you if you have either inside of a Loop.

Much better is using SObjects and Fast Update wherever possible. Pass in the "Parent" record ID from your triggering Process Builder and use an Assignment block to add that Id to an SObject of the corresponding object type. Make any other changes you need to save to that SObject using subsequent Assignment blocks (or the same one, if you don't need special logic-- but if not, why are you using a flow?), then "Commit" everything all at once using a Fast Update. Done well, you can avoid SOQL queries entirely meaning that your flow will still work and not cough up a governor limit error even if you're updating 200 records at a time via the data loader or some such.