Hi Hopeful,
A longish explanation to something that is done almost automatically, I even had to get my guitar out to write down how I play it, so here goes.
C. Thumb picks the fifth string, index finger the third string, middle and ring finger pick second and first strings together, index finger picks the third string. That is the first bar. The second bar on C is the same apart from the thumb picking the fouth string.
Fm, Am and Am7 are picked in just the same way.
D, F and Dm the thumb picks just the fourth string for both bars.
G and Em the thumb picks sixth the first time and fourth on the second bar.
I hope that is clear. Your thumb is the only finger that plays different strings.
Roger