I can't see where or how to enter a car that was donated. I've read several answers and it doesn't help me find out how.

Unfortunately, there doesn't seem to be another question asked by you under this name/account, so I don't know what you read.

I also can't tell which TurboTax platform you are using, desktop or Online.

On the desktop products (the ones that you install on your PC or Mac), on Windows, at least, go to View at the top left, click on it and chose Step-by-Step. In the upper right corner under the Refund Meter, you will see a field with the word "Find" in white on a blue field. This is the Search button.

For the Online products, on the upper right, to the left of "Help", you should see the word Search preceeded by a magnifying glass. Click on this (they are the same button) and a data entry field will open on the right.

If you received a 1098-C, then do a Search for "1098-c" (lower case and without the double quotes) and jump to it.