How will i post tweet update to all users who allow my twitter app?

I already stored oauth_tokens of all users on my database and other user info.

I only wonder on how will I post tweet update on their profiles?

Any idea guys? Please help.

Before you try to solve the technical question read Twitter's guidelines for API developers. Tweeting into the account of everyone who authorizes your account without their explicit and informed permission will get you banned from Twitter real fast. Ask them if they want to have you tweet something before doing it.