One simple way of noting down which notes to play is guitar TAB. Guitar TAB has it’s limitations but it is easy to read.
Guitar TAB appears on the page as six horizontal lines representing the six strings on your guitar. To top line is the high E (thinnest) string and the bottom line is the low E (thickest) string.
Guitar TAB is read left to right just like reading a book and the notes are played in the order in which they appear.
The line on which the note appears corresponds to the string on your guitar you should play and the number represents the fret where your finger should be on that string to sound the correct note.
A zero (0) on a line means play the string open (no fingers fretting notes).
The first note above is on the 6th string no fingers (open string).
The next note to play is on the 6th string fretted at the 3rd fret.
The next note is on the 5th string no fingers (open string).
The next note is on the 5th string fretted at the 2nd fret.
And so on working across the page from left to right.