For exchanging this cypto-currency to local or international currency we need different system like PayPal and others service providers.
There is lot of ways how to get bitcoin the first is , the what so called the buying low and selling high if you wanted to buy bitcoin at the cheep price you will go to the p2p or person to person which is the person will give you a price that you wanted and buy and either you sell it or whatsoever , but on the online just monitor the marketplace or the value of the bitcoin , if at the lowest then buy that's all then wait until it increases.
But one of the common jobs is the bounty and the airdrop which , well some of the bounties and airdrop aren't legit so better watch out okay , and my tips is to be aware , be curious on something , review it and gathered some information so that the bounty you participated in and also the airdrop you join is worth.