This excellent video by GCH Guitar Academy explains how to get started with box-1 of the C Major scale pattern and how to use it in improvisation. We are not affiliated with the creator, but if you like this video, please visit them, like and subscribe and all that :)
First what is a diatonic scale? It is simply any seven note scale that uses 5 whole steps (whole tones) and two half steps (semi-tones) in the octave. So in this C Major scale
The most common way to start memorizing the whole neck is by dividing the pattern in to a few bite-sized chunks. This lesson has divided the C Major scale pattern in to 5 boxes.
You can take all the time that you need to memorize them. So start with the first one and after a week or so, you can move on to the second. Thake it easy and set your own pace, whatever is comfortable for you!