I join in some airdrops,but theres no information about the airdrop giveaway or on the site about adding token and contract info, they just want my eth wallet.Maybe the info will be given after ICO?
You don't have to add it if you don't want to. All you have to do is input you wallet to ethplorer.io and you will see there your tokens and the dates they are added. Now if you want to see them everything you take a peek at your wallet then that's the time you will have to custom add their contacts in order for them to appear in your wallet. Also use MetaMask as advised by one buddy here to lessen your chances of getting phished.