You can participate in any airdrop campaign by following the instructions of community of cryptocurrency. Usually You can find Airdrop campaign on Bitcointalk.org, Reddit, Medium and many other bitcoin & cryptocurrency community websites. Instructions may include, by filling in the airdrop form, collecting your information related to your ETH account if it is contract base tokens or coins. If you want to participate in more Airdrop. You must be active here on Bitcointalk.org