When you receive a llama badge, common courtesy is to return the favor. To give a llama badge, you click on the username of the person who sent it to you, and it will direct you to their profile. In the right hand corner of their profile screen, you'll see a little present box that says "give". Select that box, and it will give you a drop down menu. Select "Give a Llama Badge" and DevArt will ask you to put in your password to confirm that you'd like to send the badge.
Once you have input your password, the badge will be sent!
If you have any other questions, feel free to let me know!
Have a wonderful day