A little more information would be helpful. Are you getting any sound at all out of Logic from a guitar or keyboard? How about software synths? Have you checked your audio preferences? See page 63 in your book. You'll want to make sure the appropriate output device is selected.
Don't get discouraged. You will learn a lot using the Nahmani book.
When you create a new software instrument track Logic automatically adds a software synth with a default electric piano patch. You can audition other patches by selecting them in the library on the right. If you play something on your MIDI keyboard or your computer keyboard (press the "caps lock" key first) you should hear the sound, assuming that you've selected the appropriate output device in audio preferences. Be sure that your track is "record enabled" (the "R" button will be red) in order to hear the sound.
Since your original post was about loops I should point out that there are two kinds of loops: MIDI and audio. Green loops are MIDI and Blue loops are audio. If you drag either kind of loop out into the arrange window Logic will create either a software instrument track or an audio track as appropriate to accommodate your chosen loop. When you play the track you should hear the sound through your selected audio output device.