Updated readme

Author: rickmills

README.md

@@ -2,7 +2,7 @@
 
 [![Go Report Card](https://goreportcard.com/badge/github.com/serverauth-com/serverauth-agent)](https://goreportcard.com/report/github.com/serverauth-com/serverauth-agent)
 
-This repository contains the source code for the ServerAuth Agent. A small Go based package that is used to synchronize your account SSH keys.
+This repository contains the source code for the ServerAuth Agent. A small Go based package that is used to synchronize your account SSH keys. Please note that to use this you'll need to first sign up for an account at https://serverauth.com
 
 In most cases you can use the installer provided inside your ServerAuth account, which obtains the latest stable release of the agent from Github. However if you'd prefer to build the package from source, please see below.