Communication is crucial in Valorant in order to discuss strategies, inform your teammates about the opponents' positions, make jokes during the match, and much more. While you can talk to your teammates through your mic, if you don't have one, you can find dedicated chat options that you can use in order to talk to your teammates and also the opponents.
Here's how you can chat with your teammates or opponents and a guide to changing their keybinds if you don't like the default ones.
Valorant: How To Talk In Team Chat
If you want to chat with your team, you will find a chatbox on the bottom left corner of your screen, and you can access it by pressing Enter and once you have sent your message, press ESC to exit the chat box.
Valorant: How To Use All Chat
If you want to trash talk the opponents or writer "GG" at the end of the match, you can press Shift + Enter on your keyboard to switch the chatbox to All chat. Once you have sent a message, it will switch back to the Team chat automatically.
You can also send a personal message to a teammate by pressing Enter and then Tab. You will then have to type the name of the player to that you want to send the message, and no other teammate would be able to see it.