You probably already know that playing acoustic guitar consists of pressing certain strings down against the fingerboard with one hand, and then picking or strumming the strings with the other hand.
While that is true, there are a few things to mention that may be helpful.
Most right handed guitarists use their left hand to form chords, and their right hand to pick or strum the strings.
For a left handed guitar player, it is just the opposite.
If you play left handed, you should use a guitar strung left-handed, meaning the strings are in the opposite order.
There are many stories of left handed guitarists who learned to play on a right handed guitar upside down, but it is much more difficult to play a guitar in this way.
Playing a note on a guitar involves pressing strings against the fingerboard of the guitar.
When a string is pressed, it becomes pinched against a fret on the fingerboard.
When that string is played, it will vibrate only between the fret where it is pressed and the bridge where it is attached to the guitar.
Pressing a string against a fret makes the vibrating portion of the string shorter.
A shorter string will vibrate at a higher frequency causing a higher pitch note.
Strings must be solidly pinched against the intended fret.
If the string is not pinched solidly, it may either have a muffled sound, or it may buzz.
One way to help press a string more solidly is to place your finger just beside the fret that you are playing, instead of directly in between the two frets.
You won't play guitar for very long before you realize that playing guitar hurts.
Mostly it hurts your fingertips, but it also may cramp your hand, thumb, and forearm (especially playing barre chords).
The only solution is to grit your teeth and play regularly, because that is how you will develop callouses and hand strength that will eventually alleviate the pain.