From TomatoCMS Documentation

Installing MAMP

• Download MAMP from its official website

• Unzip and click on the unzipped file. Follow the MAMP Install Wizard.
• Drag MAMP icon and drop it to the Applications directory:

• Go to the /Applications/MAMP directory, and click on the MAMP.app file
• MAMP starts successfully if you see the following window:

• Click on the Preferences button, then click on the Ports tab.

Click on the Set to default Apache and MySQL ports. Then you will see that MAMP uses port 80 for Apache and 3306 for MySQL.

Click on the OK button.

Creating the database

In this step, we will use phpMyAdmin to create the database for TomatoCMS named tomatocms, and create a MySQL user named tomato who have the full privileges to access the database.
From the main MAMP window, click on the Open start page.

• Click on the phpMyAdmin tab at the top of page.
• Enter tomatocms in the text box below the Create the database label.
• Select utf8_general_ci from the list of charsets and collations.

Press the Create button to create the database.

• phpMyAdmin will redirect you to the created database page.

Click on the Privileges link on the right. Then click on the Add a new User link

• In the Login information group,
  • Enter tomato to the field of Username
  • Select local from the Host select box
  • Enter the password and re-type it in the Password and Re-type fields
• Click on the Grant all privileges on database "tomatocms" check box
• Finally, press the Go button at the bottom of page.

Installing TomatoCMS

• Download TomatoCMS from its official website.
• Unzip, and copy extract directory to the /Applications/MAMP/htdocs/ directory:

• Point your web browser to http://localhost/tomatocms/index.php
• It will redirect you to the install page.

From now, follow this guide