How to buy Bitcoin in seconds from your smartphone...

*It's easy to buy bitcoin.
*You can spend bitcoin online and in some retail stores.
*But be warned: Its valuation fluctuates wildly, making it a risky investment.

You've seen all the headlines about bitcoin and other cryptocurrencies rising in value. Maybe you want to get in on the game. But how do you even start? We'll show you.

Before you do this, though, you should note that bitcoin isn't universally accepted like regular currency. My colleague Seema Mody published a great video recently where she tried to live a week on the currency, and it wasn't easy. You can use bitcoin online and at some retailers, but for the most part you're still better off just paying with cash or a credit/debit card.

You should also be aware that bitcoin is more like a speculative investment than a regular currency, and can fluctuate wildly in value. Although the overall trend has been up in recent months, but crashes of 20 percent or more in a few days are historically not uncommon.
Still interested? Here's how to get started:

Download the app "Coinbase."

*It's available for Android and iPhone.

Create a Coinbase account.

You'll need to agree to terms and enter the state you live in.

Now you're logged in. Look at that daily volatility!

Again, the price of a single bitcoin tends to be pretty volatile, skyrocketing one day and collapsing another. It is a speculative investment.

Add a payment account
Tap the "buy" button at the bottom of the screen to add a payment account. Credit and debit cards allow instant buys but only let you purchase $150 in Bitcoin per week. Linking a bank account can take 4 to 5 days to trade, but you have higher buying limits.

You're ready to buy. Tap the Buy button again.
This time you'll see a screen showing your account information. Since I'm using a credit card, I can only buy $150 worth per week. If I buy $100 right now at the current $2708.51 price, I'll get $0.03692073 Bitcoin. There's a $3.99 fee. Now I just tap the Buy button again.

You can also buy Ethereum
You can use the same app to buy Ethereum, another cryptocurrency. At the time of writing, Ether, the currency associated with Ethereum, is available from $327 a pop. Like with Bitcoin, you're limited to how much you can buy per week.

Prepare for the fraud prevention call

My bank called me within 5 minutes to verify my attempt to buy Bitcoin. You may face the same situation, just approve the purchases and you should be good to go.