clarify OS X release steps [ci skip]

docs/developers-guide-osx.md

@@ -78,7 +78,7 @@ cp /path/to/private/key.pem OSX/dsa_priv.pem
 sed -i '' -e 's!usr/bin/perl!usr/bin/env perl!' ./bin/osx-release
 ```
 
-You'll probably also want an Apple Developer ID Application Certificate in your computer's keychain (ask Cam).
+You'll probably also want an Apple Developer ID Application Certificate in your computer's keychain. You'll need to generate a Certificate Signing Request from Keychain Access, and have Sameer go to [the Apple Developer Site](https://developer.apple.com/account/mac/certificate/) and generate one for you, then load the file on your computer. 
 
 After that, you are good to go:
 ```bash