Can’t set iOS developer certificate

I want to get into iOS app development and at the moment I’ve only got the free developer account.

I’ve got an open source iOS app that I wanted to compile myself and get familiar with Xcode.

My issue at the moment is that my signing certificate is listed as Mac Developer and my Deployment Target options are just MacOS versions 10.6 - 10.14. I do not have the option to pick iOS Developer as my signing certificate, nor can I set an iOS deployment target.

If I go into Xcode preferences and manage certificates, I can see that I’ve got both a MacOS and iOS development certificate.

How do I fix this?