FIrst, you have chosen the right thing because QE is really amazing. Try to download, compile and install QE by your own. Then go to test and tutorial folder and open up the input files for any types of calculations and try to find out what each single command line says. Also. you may need to run some simple tests and analyze the outputs.
A nice hands on tutorial ( from ICPT during MaX School on Advanced Materials and Molecular Modelling with Quantum ESPRESSO) with explanation of theoretical background is available at the following sites.