Often, you'll send out the item donation form to ask for items and to allow donors to offer items for an upcoming auction. When people fill out this form, you'll be able to see any donated items here:

From "Item Donations", click on the three dots next to the item and then click "Create Giveaway:"

You will them be prompted to select a start and end date for your giveaway. Once you've decided on this, click "Import." Keep in mind, this can be edited later.

When your item has been imported as a Giveaway, you can then click "Edit Giveaway" to be taken to the new campaign.

Finally, you are able to edit any details from this campaign, and make it Public! Your item has now been imported as a giveaway!