Hi Adam
Glazing really just means another layer of colour or medium. What Colleen's suggesting is that you subdue the 'sharpness' of the lighthouse - to knock it out of focus, as it were. This would make the lighthouse appear to be further away than the eiders. One way to do this (I'm sorry, I assume you are using acrylics?) is to mix a very, very diluted grey/blue with lots of water and then you need to have a lot of trust. Paint the whole of the background (excluding the eiders) with a layer of this 'glaze' and, when it dries, the lighthouse will look less prominent. You can add as many layers of glaze as you like - each one will increase the effect (a bit like laying tracing paper over your drawing, time and time again - but it's really quite subtle). If you're using oils, the technique is slightly different and you need longer drying times.
If in doubt, have a bit of a practice on a seperate piece of board first. And your artwork needs to be lying flat when you do this process - otherwise the glaze will run off.
And - although you may feel you are lacking in a few techniques - you certainly have got more than a clue about how to paint.