Fretboard dots are our friend. Even for the most advanced guitar players, these visual markers can be handy to quickly identify where we are on the neck.
To learn all notes on the fretboard, a good way to start is by memorizing the fretboard dot notes on each string. After you have the dot notes memorized, you can easily find notes in between the dots by counting up or down chromatically (https://www.guitarthinker.com/lessons/music-notes).
E String Dot Notes
6th string (low E string) and 1st (high E string) with the dot notes labeled