I like it when manuals are extremely short and straight to the point. So this is the shortest I could do
- Wallets such as Coinbase and uphold are crypto wallets allow you to purchase ether or bitcoin, which in turn will allow you to buy steem or steem power directly from the block trades
Changelly is an amazing site that lets you exchange pretty much anything crypto to crypto.
More importantly it allows visa & mastercard! simply select the USD or EUR to Steem and you're good to go.