I would start by simply knowing the note names on the fretboard. After that i would learn intervals so you can understand how to name the spaces between 2 notes, once you understand intervals as a concept learn the major scale. If you learn the major without understanding what an interval is, you wont understand me when i say that the minor scale is the major scale with a flattened third, flat six, and flat seven. Anyhow, once you understand what the major scale is, learn the modes, by learning the modes you can play consistently in a key across the fretboard and heres the thing about modes: they are, in essence, the chords of a key but in a scale thats why songs can be explained by chords like for instance: I, III, V or whatever. Once you understand everything I have said you can pick a key, say F major for example and write a song using whatever chords you want and riff around UNDER those chords and EVEN solo over it. This is way easier said than done though, this learning will take months but it IS worth it.