How did the FED bought those US Bonds in QE2?

[Battleship]

The US borrows money by selling bonds to Foreign Countries and FED. For QE2, the bonds are 30% bought by foreign countries and 70% bought by FED. Could I understand that the FED bought those bonds by printing money off the machines, which is like from left pocket to right pocket right? I’m asking those questions because I understand the FEB has no surpluses saving, so was thinking how the FED purchased those bonds.. Hope to hear from the rest with the knowledge. Thanks.