The first time you try to play chords and notes you may find it frustrating. This is because your hands and fingers are not used to being used in this way and it may take a while to build up the right muscles and increase suppleness. And if you do a long first practice, your wrists and fingers may feel a little stiff the next time. Don't let this stop you. It won't be too long before your fingers are strong and agile enough to tackle the most difficult riffs and licks.
Notes differ from chords in that only one single tone is produced from one string. If you are playing chords, then you usually use three or more notes to produces the tone. When playing a note on a piano, you press one key; when playing a note on a guitar, you push down one string onto the fret. If you pick the low E-string without fretting, you would play the E note - assuming your guitar is properly tuned.
When you use the first fret with the E-string you will produce an F note. The second fret will give you an F# (# =sharp). The third fret on the E-string gives you the G note; the fourth fret G# and so on up to the B note. Note that there is no B# or E#.
There are many ways in which to produce each specific note on the guitar, so it's a good idea to learn to read the tablature format, or guitar tab. This is a way of writing guitar music that is easy to read, as it resembles the strings of the guitar. The guitar tab shows which fingers to use on frets.
To hold your fretting hand in the correct position for playing notes, you need to start with your thumb. The ball of the thumb should be positioned flat on the back of the guitar neck, like you were trying to make a really good thumbprint on it. Curl your other four fingers around and up over the strings, touching the topmost (thickest) string lightly. Get them to feel comfortable without allowing them to brush against the bottom (thinnest) string. You can change your thumb position now to make it the most comfortable.
When fretting, don't place your fingers directly on the fret. Use your fingertip to push the string against the fret, but keep your finger slightly to the topside of the fret. Practice this by holding all four fingers just on the topside and above the first four frets on the top (sixth) string. Pick the sixth string, then lower your index finger onto the fret (just above it, remember) and pick the string again, noting the difference in the sound. Use the other fingers in a similar manner. Remember, it gets easier with practice.