As you move from the C chord to the G7 chord the 2nd and 3rd fingers move in the opposite directional path that the first finger takes.
Ok now the viewer is aware of the finger relationship movement between the C and G7 chord.
When we strum a chord, we move from the lowest sounding strings of the chord towards the highest sounding strings of the chord. This is in a physical downward movement towards the floor.
Set the C chord
For the raw new beginner, after you have the C chord set, with the fingers down behind the frets in the C chord shape, make 16 strums on the C chord with the right hand doing the strumming. As you make each strum, the chord should sound.
After each strum, release the pressure of the fingers on the strings, but keep them set on the strings, ready to come back down on the strings hitting the fingerboard behind each fret, on each additional strum. There will be 16 strums with the fret hand fingers doing a sort of dance.
The 16 strums make up 4 strums per each 4 beats. That comprises a measure with 4 beats, 4 strums.
Now do the same process with the G7 chord. Strum 4 times. After each strum release the pressure on the strings between each beat, but ready to come down on the next beat. Four beats for each measure and attack on each beat with the fret fingers behind the frets
With a little practice, start to attempt to make the changes from the C chord to the G7 chord without breaking the rhythm of the strumming. Don't worry if you can't get all the fingers set quickly, keep strumming. That will sort of force you to get the fingers in position.
Even though you don't have the changes down smoothly yet, go to the next page for part II of the chord changing process. You will rotate through the various parts of chord changing practice. In time it will be smooth.