When you want to send your heartbeat on Imessage, there are a few different ways that you can go about doing it. You can either use the built-in Heartbeat feature in Imessage, or you can download and install a third-party app that will allow you to do it.
If you want to use the built-in Heartbeat feature in Imessage, all you need to do is open up a conversation with someone who also has Imessage. Then, tap on the heart icon at the bottom of the screen and hold your finger down. Your heartbeat will then be sent to the other person!
If you want to download and install a third-party app to send your heartbeat on Imessage, there are quite a few different ones that you can choose from. One popular option is called Heartbeats for iMessage, which is available for free from the App Store. Another option is iHeartbeats, which is also available for free from the App Store.