This broker offers that. You can open a free demo account to practice. You can download their app onto your smartphone and tablet too to place trades.
They also provide lots of free information on how to place trades and they will talk you through it on the phone too.
I like them because I've met them, they are FCA regulated in the UK and SEC regulated in the US and also regulated around the world and are listed on the New York Stock Exchange - so big.
You can use them as an American or from anywhere.
I also like these brokers but their minimum trade size is larger: