Your site has an embedded Donation Form to allow donors to submit their donation online. The Donation Submission Form does not need to be turned on - all you need to do is edit the default introductory text and confirmation email message (if desired) and then send invitations to donate and/or advertise and distribute links to the URL.
2. Review/Edit Confirmation Email
Go to Site Settings > Customize Your Site > Email/Text Messaging > Email Templates > Online Item Donation Confirmation
3. Personalize Donation Form
In addition to customizing some of the field descriptors (see above), you can also add custom fields.
Instructions for Managing Pending Donations.