How do I turn on my mic?

I have an app that need access to mic and there is no way to turn it on!.!.. when I go to mic it show app that have requested it but the are dark and can not be changed. The new app I have is no on there and I have no idea on had to give it access to it. Why the **** does this have to be so hard to do?? It used to be when I installed an app it asked and I granted access now you all have gone and screwed that up along with so many other thing that makes no sense!!!!