NOTE: "Team Chats" are Push Notifications. Unlike text messages, which go through a mobile carrier, push notifications are sent/received by your phone's operating system.
Within the Home tab, tap the Chat button in the team you wish to message.
Enter the desired message.
To include attachments, tap the camera icon in the message bar.
Once satisfied, tap the paper airplane icon to send.
Helpful Tip! GIFs can be a lot of fun. Unfortunately, not all GIFs will work as expected in team chats currently, particularly when using iOS. GIFs saved from another app or from a website onto your mobile device have the best chance of creating the desired effect.