Hi, I have developed an application reserved for members of one of my clubs. Members who have an Android phone can download the application with a link. How can I get iPhone owners to install the application without having to add it to the appstore? The app is free and I wouldn’t want to pay to have to distribute it to about a hundred members. Thank you
send them a TestFlight link
If you do an internal test in TestFlight, you do not have to add it for review by Apple, either. Another huge advantage to TestFlight.
Thanks for the info . But do I always have to sign up for the Apple Developer Program? And then pay $99 every year? 
The app I developed is free and only for friends who are members of a club.
If you want to have your APP on the iphone YES you need a developer account