Sealing, Priming, and Painting a Window
First advise is not to use any "sealer" on window frames. Paint won't normally adhere well to wood sealers.  If possible, I like oil based exterior primer, even two coats so your frames are well covered.  The you can use any good latex exterior trim paint.  Remember, prep is very important, and you cannot use oil based primer over any latex, so if you have latex, you must use latex primer or BIN's Bullseye pigmented shellac.