A complete newbie question here but how does one simply buy 43...

A complete newbie question here but how does one simply buy 43 million shares when there is not that amount for sale? Does the company approach investors for them? I bought this stock at 14 cents thinking it was a good proposition but if the company is prepared to buy them back at 21 cents I'll take the profit. Does the company just buy them all at on once? Thanks in advance for any explanation.