Here are the steps to split an unmerged cell in two:

1. Select the cell that you want to split.
2. Click on the "Layout" tab in the ribbon at the top of the screen.
3. Click on the "Merge & Center" dropdown menu.
4. Select "Split Cells".
5. In the "Split Cells" dialog box, choose whether you want to split the cell into rows or columns.
6. Enter the number of rows or columns that you want to split the cell into.
7. Click "OK".

And that's it! Your cell should now be split into the number of rows or columns that you specified. Keep in mind that any data that was in the original cell will be split up into the new cells as well.

I hope that helps!