Help with pages (apple iwork)?

I take it you aren't very experienced with word processors yet. The underline tells you it's wrong. Right-click, hold down control and click, or two-finger click (if you're on a Mac laptop with a multi touch trackpad) on the word and you'll see the suggestions. To run the spell check on the entire doent, either Press Command-: or go to Edit->Spelling->Check Spelling.