You can turn on the donation feature by following the steps in this guide!

This feature still needs to be tied to a ticket type, so in reporting it'll be shown under it's respective event under the ticket name you supply.

• Login to your Ticket Socket admin page of your site
• Click on Settings > Site > General 
  • Toggle on "Enable Donate Any Amount"
• Go to your event manager and select event you wish to add donations to
  • Events > Events > "Actions/Wrench" Icon and Edit
• On your events page click on the "Ticket Types" tab
  • Click on "Add New"
  • Name it accordingly
  • Price MUST be set to 0
  • Set Shipping to "Disabled"
• Create that ticket and click on the "Edit" button to the right of that ticket
  • Click on "Advanced" 
  • Toggle on "Hide in Front End"
    • This is important to do so customers cannot view the ticket by itself. A ticket needs to exist in order for checkout to occur, so creating a ticket type is mandatory.
• Save your changes!
• Click on the "Donations" tab of your event editor
  • Toggle on "Donate Any Amount"
  • Select the donation ticket you just created
  • In the "Preset Amounts:" field enter in amounts desired, separated by commas
    • Example: 5,10,20,25,30,50,100
• Save your changes and you're all set!

Below are screenshots helping you through this process and a picture of the donation modal during checkout!