This item will refer to the Help item on setting up Salesforce Lightning.  There are just a few small differences:

This the link to the Lightning Help page.

Check your Edition

Getting to Setup is slightly different

the Administration Setup > Company Profile > Company Information is the place to go in Classic to check your Organization Edition says Enterprise Edition.

Setting up the MeetMax "App" in Salesforce

Stay in Setup and go to
Administration Setup  > Create > Apps
then at the bottom section on Connected Apps, click New

Username and Password for the integration

When logged in as the Admin user associated with the account that set up the MeetMax api, Setup, go to

Personal Setup > My Personal Information > Reset My Security Token

The rest of the steps are identical to Lightning.

Check the Permissions of the User

Still in Setup

Administration Setup > Manage Users > Users

Then when you see the list of Users, click on System Administrator (for any user who is one).  This takes you to a page just like shown in Lightning, to check that the System Administrator is permitted to use the MeetMax Connected App

That completes the basic 1-time setup in Classic.