Hi all!
Great forum you got here, it's been very helpful.
I just recently (unfortunately!) got into crypto currencies and my understanding on blockchain is very limited.
I recently bought into interesting ICO using MEW. Creating and funding the wallet was easy and everything went without a problem. The question is, if I now want to join other ICO, is there any issues using the same wallet for the future ICOs or should I create new wallet for each I want to participate? Receiving the tokens is still something I don't fully understand and if someone could ELI5 to me I would be grateful!
You can always use the same wallet. There is no issue about re-using it. But you can also create as many wallets as you want (maybe for privacy reasons or something like that).
The only thing you need to worry is about security. I don't know if it is better for you to put everything in the same wallet (and if you lose one key you lose everything) or if it is better to use different wallets and have to manage a lot of keys.
About receiving the tokens:
Since you used MEW, I assume you bought some tokens that are Ethereum-based, using the ERC-20 standard. Ethereum-based tokens include BAT, GNT, SNT, ZRX, OMG, PAY, etc. Those tokens are defined in a smart contract registered in the Ethereum blockchain. Usually, the ICO smart contract sends you the tokens immediately when you send ETH to the contract and you can see them in Etherscan or MEW.
When you are using MEW, in the option "Send ETH & Tokens" there is a drop-down menu to select which token you want to transfer.. if you need to sell tokens you bought from an ICO you should carefully copy the corresponding deposit address in the exchange and send them using MEW. Alternatively, you can use a decentralized exchange such as EtherDelta where you can trade straight from your wallet.
Of course, there are different kinds of ICOs, some might not use Ethereum or might not send you the tokens in the moment you send the ETH. I am explaining the ones like the above mentioned and Auctus, which I am one of the members.