As Zurf said, thinest string is your 1st string, thickest string is your 6th string, the fret nearest the top is the 1st fret. Chords played individualy just sound like a chord, but played in a group sound like a tune. Learn this:-
C chord.
1st finger, 2nd string,1st fret
2nd finger,4th string, 2nd fret
3rd finger,5th string, 3rd fret
Am chord.
1st finger, 2nd string, 1st fret
2nd finger, 4th string, 2nd fret
3rd finger, 3rd string, 2nd fret
F chord.
1st finger, 1st & 2nd string, 1st fret,
2nd finger, 3rd string, 2nd fret
3rd finger, 4th string, 3rd fret
G7 chord.
1st finger, 1st string,1st fret
2nd finger,5th string, 2nd fret
3rd finger, 6th string, 3rd fret
Put your 1st,2nd, and 3rd fingers on the frets as indicated, learn C, then Am, then F,
then G7, once learned, play C then Am, then F, then G7, this group of chords fits loads
of songs and tunes, best of luck, let me know how you go on. Tony.