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- Under section Platform Tools → Expand Users
- Click New (or reuse existing, don´t click new view)
- Enter a name such as API
- Click System Permissions
Check API Enabled and Apex REST Services
Expand title Click here to show image... Click on Users
Click on the user that you will use for API access
- Scroll down to Permission Set and edit. Assign the new API permission set to the user
Save and all done!
Expand title Click here to show image...
Some resources
Assign Permission Sets to a Single User
How Do I Enable API Access in Salesforce Lightning Experience by the Permission Set?