Honestly, when a song is written with the chord above and no beat markings, there really is no way to know how the song is played nor even what the time signature is. But the good news is that if you know the song well enough to sing it, you can generally use these very simple song “charts” to come up with a decent if not accurate representation.
Let’s take your example of WTCBU.
If you look carefully at the tune, you can see that the chord markings are written directly above where they would be used. For example, the chord “G” starts the tune and is played until the chord “C” which is played when you reach the word “cold”. Then “C” is played until you reach the word “day” where you change back to “G”.
Now, if you pick a simple strum as the rhythm (Bass-Strum will work nicely), you can play this strum in an even time until you reach the word where you would change the chord to the one marked above that word.
Be aware, if these simple “charts” are accurately written, the chord will fall directly above not only the word where the chord would change, but above the syllable. For example, in the second verse, second line, the chord “C” correctly falls on the 3rd syllable of the word “undertaker”.
The only other concern you may run into is if you know the song, but have a hard time figuring out the starting note of the melody, given the chords that are in the chart. This is a matter for another topic, but I can tell you that you can often hear what the “key” of the song is just by playing the chords given and speaking the words rhythmically in time with the chord changes.