You have two options:
(1) Go to File Handling preferences and choose Create Links When Placing Text and Spreadsheet Files. Do all your formatting in Excel and import the formatting by choosing Show Import Options.
If you do formatting in InDesign, it will be thrown away when you do an update.
(2) Turn on those preferences. Do the formatting in InDesign, knowing that you'll have to re-apply it when you do an update. Carefully create Table, Cell and Paragraph styles to speed up the formatting process.
That is what I did originally and it was thrown away when I updated. I thought I did it incorrectly. I'm not sure if I understand how to format in excel?
Formatting in Excel probably isn't usable for most people. It doesn't have the refinement of InDesign formatting so the second choice is by far the best.