You can claim the cost to set up your pension plan as an "Other miscellaneous expense" on your schedule C.
In your schedule C:
When you get to the screen that asks "What kind of expenses did you have for <your business>?", choose the drop-down for "Less common expenses" and select "Other miscellaneous expenses"
Click "Continue"
Scroll down to Expenses; find "Other miscellaneous expenses"; click on the blue Start button
Enter a description such as "Pension administration" and enter the expense
