In the upper left corner, open the navigation menu by tapping the hamburger icon.

Tap Membership.

Tap Accounts/Members.

Using the checkboxes, select the accounts to message.

Tap Message.

Select the message type, and tap Compose Message.

Type in the message, or Use Canned Message.

Tap the relevant icon to attach a video, photo, or PDF to this message.

Tap Send Message.