The ABC language is not very tolerant against syntax errors. Moreover, ABCExplorer fails to report any syntax errors, even if the underlying software does diagnose them. Therefore, your best bet is to get those tutorials and read them.

The easiest way is to have each V: field have a line of its own (you can add a clef etc.), followed by all the notes of that voice. Make sure to put a K: field directly preceding the first V: line. Use arbitrary but distinct names behind the : of each V:.

Also make sure to erase any space character at the beginning of any line - some browsers add these when copy-and-pasting.

X:1
T:C Major
M:4/4
K:C
V:soprano
c8 |]
V:alto
G8 |]
V:tenor clef=treble_8
E8 |]
V:bass clef=bass
C,,8 |]

If you are still dumbfounded, give us an example of what you tried.