I am trying to enter numbers into medical expenses and the program won't let me.

Which TurboTax program are you using?  

The TurboTax online web-based editions?

Or the TurboTax desktop CD/Download editions installed on your computer?  If the desktop editions, which operating system are you using, Windows or Mac?

Does the expense box you are trying to enter in have a pre-filled 0 in the box?

Medical, dental, and vision expenses are reported on Schedule A and entered in the Deductions & Credits section. In TurboTax Online:

1. With your return open, search for Schedule A and then select the Jump to link in the search results.
2. Enter your medical expenses, starting with prescriptions, on the following screens.

See this help article for more information.

If a screen in TurboTax Online isn't responding, check your Internet connection. Logging out of TurboTax and back in, changing browsers (Chrome generally works well), or clearing your cache and cookies often helps. 

@pamcuddeback