The shortcut Alt+Enter is to start a new line in the same cell.
Step 1: Double click the cell and move the cursor to the end of the content in the cell (e.g., B3);
Step 2: Press and hold the "ALT" key, then click the "Enter" key from the keyboard, the cursor will start a new line;
Step 3: Type the words and press "Enter" key to move the cursor out of the cell.