If you are in Lightning and you are trying to figure out where to set up the Lead mapping of fields to Contacts, Accounts, and Opportunities, follow the steps below.

1. Go to Setup
2. Click on Object Manager and search for Lead
3. On the Lead page, in the top right, there is a button that is called Map Lead Fields – click on that

4. Set up the mapping as you need and click Save!

That’s it!