Depends on what youre using it for....

The most common use is to attach detail of stock transactions.  

IF that's is why you need F 8453, it's generated by marking in the dispositions screen that you'll be attaching the detail instead of entering numerous transactions.

IF you need it for something else, let us know.

Need to activate 8453 for sending 8332 to IRS in mail

Enter the 8332 info into the program. The 8453 will generate and print. Or at least in the past it has. Have not had to print one this year.

Why not attach it as a pdf?

If return has been rejected because of a disputed dependent is a very common problem. Return must be mailed. 

But then you're not using the 8453. You're sending the form with the 1040.

You are correct. That is what I get for late night thinking.