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’m a physician - am MD. As long as I don’t get burnt at the stake for witchcraft, I could go back as far as I wanted. People’s biology hasn’t changed much since Neolithic times.
Be a shame you can’t make medicines though
Just washing one’s hands before touching the patient would make a massive difference, alcohol is pretty abundant, willow bark tea for the pain (and contact your local herbalist for other remedies), you could infect people with cowpox to vaccinate them against smallpox, you might even be able to grow some penicillin if you manage to make some rudimentary Petri dishes out of broth or beer wort and happen to have the right spores floating around…