Do I need to write it manually before I mail it in? or is the form filled out correctly from using the TurboTax itemized deduction part and I only need to sign the form?
Form 8283 should have the Organization Name, Address, Date of Donation, and Amount pre-filled from your entries, so you would only need to mail it.
If yours is not showing that info, go back and step through the Charitable Donations interview screens again to check your entries.
Here's more info on Form 8283.
I went through each section again. Everything is in TurboTax but when it printed or saved again it only filled out the name and amount on the form. I’m scared to write it manually and it be wrong and rejected.
If the total amount on form 8283 is less than $500 then you don't need any of the information to be filled in. If it is greater than $500 you do. But you should still be able to file the return electronically.