Mitosheet expects you to enter a formula.

Double click the cell you would like to edit and enter a formula. The different available formulas will appear as you write.

Examples: TEXT('abc') - will put the string 'abc' into the cell. FLOAT('3.4') - will put the float 3.4 into the cell.

Set "Edit entire column" to "Off" if you just want to change the cell you are editing. "On" will change every value in the whole column.