When this question was posted MAMP did not support MySQL 8.

There is support for MySQL 8 now and with Mamp PRO I was able to get things configured properly directly in MAMP.

First MAMP Pro Settings > Server > MySQL tab. I selected the following settings:

Then to open my local DB I go to the MAMP Pro Databases tab, highlight a database, and then click "Open In" and choose my desired DB program.