Select a blank cell, and then on the Insert tab, click Symbol. At the bottom of the dialog box, type 2022 in the Character code box. Then click Insert, and Close. If you need another bullet on a new line underneath, type ALT+ENTER and repeat the process.
If you have a numeric keypad on the right side of your keyboard, press ALT+7 for a bullet.
Different fonts provide different symbols. If your font does not provide the bullet, try selecting a font such as Wingdings in the Symbol dialog box. Then enter character code 159.
You can copy and paste a bulleted list from another program, like Word. By default, it will put each bullet in its own cell. But you can also double-click a cell, and paste the whole list into the cell.