I think before you jump into Fuse ESB, you need to learn core java skills. From what you are asking, it is apparent you are new to java. You have to learn to walk before you run.
Buy a book on MyEclipse. Download it and run the examples. Now write a few projects on your own using core Java.
Next, try out the J2ee APIs. Buy another book on j2ee and start testing out the examples. Now write a few projects on your own using Spring framework. I think if you learn the Spring framework before you tackle Fuse ESB, you will be successful.
Third, you may proceed to Fuse. Hopefully by this time things will make sense.
What you are asking is like learning how to do surgery before you have completed your high school certificate.
Good luck to you.