In the BeetClock menu, select Enter time worked. On this screen, select the crop you worked on and the job you did in the dropdown menus. Then enter the number of hours (decimals are OK), and the number of workers involved in the text fields.
You can also add one or more pieces of equipment that were used. Add equipment by selecting it on the dropdown menu and tapping the + button.
Finally, if the job was not done today, select the date when the job was done by tapping Select a New Date, using the spinners to pick the month, day and year, and tapping Select Date.