How to tune a guitar to C standard tuning?
Given the tuning is “C standard” (this includes what most musicians call Standard Tuning), every major third on the guitar matrix must be tuned down one half-step.
A step is defined as moving a string from whichever fret, without pressing down another string on that same fret; for example, starting with an open A note and stepping to B♭ at the second fret on string 1 going to C ♯ at the 3rd fret of string 2.
The notes you need are D♯ (2nd) E♭ (5th) G♯ (7th) A♮ (8th)—and when playing those notes in descending order from lowest to highest—the order will sound like this: A♮ E♭ G♯ D♯.
So if you have a guitar with 24 frets, the last 2 notes are the same note, so you’ll need to get a capo for your guitar. This means that if this is your first time tuning your guitar, then get a capo. (Capos are cheap and it’s not worth the headache).
These two notes at frets 22 and 24 with the capo are:
A♮ E♭ G♯ D♯ A#