To expand a bit on what Duwop has posted; The round piece or button that your foot would press is screwed on. On the backside of the button is a 3/4 hex, so get a 3/4 wrench or crescent wrench and unscrew the button. Then just slip the boot down over the shaft.
Kent

1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix