Basically the title, you need to use the skills you have now and be a productive member of society.
I don’t mean go back and show the wheel or try invent germ theory etc.
For example I’m a mechanic i think I could go back to the late 1800s and still fix and repair engines and steam engines.
Maybe even take that knowledge further back and work on the first industrial machines in the late 1700s but that’s about it.
I think my knowledge of first aid and basic anatomy would be of some use in any pre-modern time period. I know enough to make a positive difference at least (wash that cut, dont drink water from downstream of your encampment, give the sick plenty of fluids, etc)
Beyond that, i’d be behind everyone else. I can fish, forage, garden, cook, start fires, and build shelter, but so could everyone for most of human history. I could probaby keep up with a hunter-gatherer society, but i’d be the least capable among them.