It is there just a little hard to see.
In the File section of the program after selecting to e-file the return, when selecting Direct Deposit for the Federal Tax Refund, on the bottom of the section will be a statement and a check box. Check the box.
The statement reads - I would like to split my refund into more than one account OR I would like to purchase U.S. Series I Bonds for myself, my family, or someone else