To use AirDrop to send files, open the "Share" button in an app, tap the AirDrop button, and select the device you want to share with. On a Mac, use Finder and go to "AirDrop" in the sidebar to manage AirDrop settings. 

Here's a more detailed guide:

On iPhone/iPad:

Open an app and select the item you want to share. For example, in the Photos app, you can select multiple photos.

Tap the "Share" button.

Tap the AirDrop button.

Select the AirDrop user/device you want to share with.

On the receiving device, a notification will appear. Accept the transfer.