The easiest / best way is to let your volunteers do it. Whenever someone signs up for an event they are automatically added to your database. You can also manually add volunteers to the Database one at a time.
You can also bulk add volunteers to the Database. To do this go into the Database menu | Participants tab and click on the Bulk Add button. Here you can copy and paste info from a spreadsheet 50 volunteers at a time. Then click on the Add button.