A cryptocurrency is a digital asset designed to work as a medium of exchange. Cryptocurrencies use decentralized mechanism as opposed to centralized banking systems. The decentralized control of each cryptocurrency works through distributed ledger technology, typically a blockchain, that serves as a public financial transaction database (paraphrased from Wikipedia).
Wallets are associated with addresses and allow people to send tokens or cryptocurrency to other addresses on the blockchain. An address on the blockchain is a public-facing account identifier which anyone can see and provide a place where anyone can send funds. Wallets, on the other hand, give a person access to the private aspect of the account which controls spending the assets contained in the account.
Thus the starting point is to get an ERC20 compatible wallet and with it establishing ownership of an account on the Ethereum blockchain. MyEtherWallet and MetaMask are both great choices and allow easy on-boarding including ways to directly acquire Ether (or ETH, the currency of the Ethereum blockchain) and, from there, buying any other blockchain-based digital asset, including of course, Cannabium.