FieldTrip is a toolbox that contains a set of separate (high-level) functions, it is not a program with a graphical user interface. The toolbox functions can be combined into an analysis pipeline, i.e. a MATLAB script containing all steps of your analysis. For this reason, if you are new to MATLAB or EEG/MEG analysis, FieldTrip might not be the way to go for you yet. If you are persistent and eager to learn, references to review papers and teaching material might help you on your way.
By far the best way to get started using FieldTrip, is by reading through the tutorial documentation, the walkthrough and through the other documentation. If you have questions that are not answered by the documentation or in the FAQ, you can register on the email list and ask the other users and the developers for help. Also, FieldTripping is not something you do alone - inform yourself about colleagues that use (or want to use) FieldTrip.
We organize FieldTrip workshops and a yearly “Advanced EEG/MEG analysis” toolkit course at the Donders Centre in which we lecture and give hands-on training sessions. Attending one of these will probably benefit your understanding and analysis skills.
If you are very eager to get started with your own data, please proceed to the user documentation section on importing your own data.