This transformer has three windings; one primary, and two identical secondaries.
Just parallel the two secondary windings (observe correct polarity, both windings same direction) , and you will have 9V at 4.4A. This will require a full-wave bridge for rectification, with a loss of TWO forward diode drops.
Or, connect the two windings in series, ground the center tap, and use only two diodes to full-wave rectify. This has the advantage of using two less rectifiers, and having only only ONE forward diode drop.
Your choice.