how do I pay taxes on money I make online?

How do I pay taxes on money I make online?Do I pay at the end of the year or do I have to fill out some special form?

You must make estimated tax payments on April 15, June 15, September 15, and January 15 if you expect to owe more than $1,000 in tax for the year. Otherwise, you would pay the tax when you file your return. For the details and exceptions, see Publication 17, which I mentioned in your earlier post.