Try to remember the notes on E string all the way to 12th fret. Then you’ll already know notes on two strings cause there are two E strings (low and high). Then when you are comfortable with that you can start learning the A string. After that you can connect low E string with D string and A string with G string. What I mean by that is that notes on D string are 2 frets up the neck from the notes on E string ( 5th fret on E string is the same note as 7th fret on D string, 6th fret E string is the same note as 8th fret D string and so on) and same thing with A string and G ( 5th fret A string is the same note on 7th fret G string). Then you just have the B string left which you just have to memorise and thats it. That’s how I learned the fretboard, maybe it will help you. Just take your time, it took me a while to memorise all that but eventually I learned it.