Sadly, neither your Laptop or your iPhone has built-in ANT+. so you will need additional dongles to allow them to connect to your ANT+ rebroadcasted signal. All of the details about the dongles needed for different setups are outlined here in this article: ANT+ Connectivity.
Your laptop will be the easiest path to setup ANT+ since you will only require an ANT+ USB dongle. You can buy a compatible dongle at the link below:
Garmin ANT+ Stick
Be sure to follow the instructions on rebreoadcasting your watch signal as well. @Mac2k3 linked it above, but I’ve linked it again here. This step is crucial, and you will not be able to connect HR without following the steps outlined in the article.
I hope this helps 
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