Using Cloudformation, this refers to adding your layer arn to the Layers property of a AWS::Lambda::Function resource. Update your functions handler to point to the newly attached layer in the console ...

Note: redis-py 5.0 will be the last version of redis-py to support Python 3.7, as it has reached end of life. redis-py 5.1 will support Python 3.8+. For faster performance, install redis with hiredis ...