If you use the iCal one, import to iCal, make sure its set to sync in iTunes, the next time you plug your iPhone/iPod Touch in it will sync up, or if you use mobile me I believe it syncs over the air instantly. Thats on a mac anyway. I don't have a Windows machine with iTunes on in front of me, but if you look at the sync options (click the phone in iTunes) it should give a list of programs to sync from, then just tick the relevant box.