The word "voila" is a French interjection that means "there you go" or "here it is". In English, we generally use it as an exclamation of surprise or triumph.
While the French spelling includes an accent aigu (é) on the "e", the word is often spelled without it in English. Both spellings are considered correct.
So, you can spell it "voila" or "voilà", and both are acceptable.