The action is set by adjusting the the height of the bridge saddles. You may find that the neck relief needs to be adjusted as well. There are threads on this site that explain these things more fully, (use the search icon at the top of the page), but I strongly recommend that you get a guitar tech to do this for you. (S)he can explain what needs to be done and how it works. You can seriously mess up a guitar by not knowing what you're doing.

As for 'the harmonic thing', the twelfth fret is at the mid-point of the string, so the note there is one octave above the open string note. The harmonic played at this point should match the note played at this fret. If it doesn't, then the intonation needs to be adjusted. This also involves adjusting the bridge saddles, so the tech can look after that while they're lowering the action.

Don't worry about what people might think about your guitar. It may not be the best in the world, but its the best one you've got, and for now, thats good enough. My first few guitars weren't as good as your Squier, so relax, learn, and enjoy.