This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I suggest the first thing to do is to get familiar with how to make web applications in general. Jumping straight into web service architecture without understanding simple client - server systems work would just be confusing.
The obvious first step would be installing Tomcat on your local system and working through some examples.
Since most of the Java web service packages work with Tomcat this is a good start.