Click the cell where you want the bullet
Press Alt + 7 on the numeric keypad
Press Alt + 0149 on the numeric keypad
Hold Alt and type 7 on the numeric keypad
Copy and paste a bullet character from another source
Use Insert > Symbol and choose a bullet character
Type =CHAR(149) in a formula if you need a bullet in a formula result
On Mac, press Option + 8
Use the Bullets option in a text box or shape if working outside a cell