To get to the chat screen from the home scree, you swipe left, or tap on the icon on the bottom left.
Here you get a list of your chat conversations.
To start chatting, tap on one of the chat threads. You can then instantly start typing your message to send, or use one of the other messaging options (upload a photo, call, take snap, video call, or send a sticker)
Friend has joined conversation
If your friend opens your chat thread while you have it open, you'll either see a smily face emoji, or their "Bitmoji". In this case, you see Ramy's bitmoji, which means he's opened the chat thread too.
To send a snap in the chat conversation, tap on the circle icon in the middle. This launches the camera so you can compose your snap.
Once it's been sent, you'll see an indication of whether it's been opened, replayed, or "screenshotted".
The focus of the stickers section is "Bitmoji" - These are stickers that you can make of yourself. You need to download a separate to make them though, so we skip that here and just use the default stickers.
To send stickers, you just tap on them. There is no confirmation step.
Tapping on the burger menu icon in the top left of a chat thread reveals a menu that lets you edit your friend's name or block them. You can also see some information about them here.
Chat thread icons
The icons on the left of each chat thread indicate the status of the conversations. For example, the blue arrow icon next to "ramy" means he took a screenshot of our last message.
The purple square from Team Snapchat means we have an unread snap from them.