Christina Lin, a Fuse evangelist, has created a great blog series of how to get started with JBoss Fuse.
She has done a great job of creating real life use-cases and detailing how to do this step by step, in both text and slides.
JBoss Fuse Blog Series by Christina Lin
People who are new to JBoss Fuse is encouraged to take a look at this, as IMHO its easier to follow an use-case, than reading through then 100s of pages of reference documentation that is part of the product.
As Apache Camel is a corner stone of JBoss Fuse, then its often also even easier to get started by just learning some basic Camel first without thinking about Fuse / App Servers / OSGi / Karaf / Blueprint / Fabric / and many other concepts that JBoss Fuse brings to the table. Learn some Camel skills, which you can easily run on your computer locally, from within your Java editor. And then only thereafter take the leap and dive into the world of JBoss Fuse.
To get started with Apache Camel I point people to read this article written by Jonathan Anstey several years ago (don't worry the information is today 100% up to date, as Camel is table and dont throw you under the bus by frequent changes) which really captures well what Camel is and what it can do. For example the foundation of Camel which James Strachan laid out 8 years ago is still the road we travel today. If you are looking for other explanations what Camel is, then there is a good QA on stackoverflow.
Another great starting point to learn Apache Camel is chapter 1 of the Camel in Action book. And this is not the only Camel book, in fact there is 4 known books published.