Step 1: Click the blue Compose icon in the lower-right corner of your chat or location screens
Step 2: Select "1-to-1 Chat" or “Group”
Step 3: Choose your contact(s) or type in the ID number they used during account creation. Note: This is likely to be their phone number — and if they're in your contact list, you'll see that clearly — but it can also be a GID, or goTenna ID, a randomized string they need to share with you
Step 4: Type your message
Step 5: Hit "Send"