The "donate_to" field is used to designate which participant should receive credit for the donation. This column on your .csv file should contain the Supporter ID of the participant that the supporter has chosen to donate in support of.

Note: You can find the Supporter ID of a partcipant's contact record as follows:
  1. Go to Contacts > Individuals
  2. Search for and locate the individual
  3. Hover over Manage and click Manage Contact
  4. Click the Profile tab
  5. Click the Personal sub-tab
  6. In the center column, under Identifiers, note the Supporter ID