where to create wallets and how to manage them (I mean safety issues)?
To create a wallet for BTC, Blockchain.info is the good one and there is have more security like connect with email, password pharekey, email verification when login,2-step verification and other. To learn it, you can learn from youtube or website tutorial do not feel enought with 1 or 2 tutorial. But you have compare some tutorials and practice it.
For ETH Wallet, i use myetherwallet.com.
After have wallet. You must join exchange like Bittrex, Bitstamp, etherdelta, bit-z or others. Exchange is the place for doing trade. Hope this helpfull for you.