When creating / editing your spreadsheet,
select a cell
at the top of the screen, you will see the bar for typing your data or a function. That bar is labeled "Type here" in light gray text.
to the left of that bar, you will see "fx"
if you click the "fx" (which stands for functions), a drop down list box will display a list of recently used functions.
if you scroll down that list, you will see a complete list of all available functions, grouped by type of function.
Additionally, the ribbon bar appears at the top of the screen. In that ribbon bar, you will see "formulas."
click on "formulas" and you will see a row of types of functions, as well as "recent" functions and "..." for other types of functions, as there are too many types of functions to display all of them on the ribbon simultaneously.
Hope this helps!