Did you follow the instructions on the second page of this topic? See here: http://community.skype.com/t5/iOS-iPhone-and-iPad/Can-t-access-microphone-on-iOS7/m-p/1919301#M22123
If that didn't help please share some more details on your setup: which device, iOS version, Skype version, description of what you did, what happened and what you had expected to happen.
I'm having the same issue except when I go to setting>microphone> skype doesn't even show up. I check to make sure I had the latest version. What should I do?