Yes, you are allowed to steal ideas. That's because you can't copyright an idea. And what I do with an idea might be very different from what you would do.
Now, there are some common sense boundaries. If I tell you I'm going to query a specific editor about an article on an upcoming event, and you quickly fire off an email to the same editor about writing an article on event, that is definitely a no no. And anything that has been published or produced is protected by copyright.
But on less specific things, stealing ideas is allowed. For example, if I read an article on how to raise great kids in a magazine, and I find that I have things to say that weren't said in the article, there's no harm in my writing another article on how to raise great kids using my perspective and my own examples. No, you can't combine three of the first author's points with two of yours. What you write has to be different, has to be uniquely yours. Other wise you're guilty of plagiarism.
So you write a totally different article, but with the same overall focus—how to raise great kids.
Now, what do you do with it? Well, unless raising kids is the primary focus of the magazine, I probably wouldn't send my article to the same magazine where you read the original. At least not for a few months. Why? Because they just published an article on that topic. And they likely won't publish a similar article for at least several months, probably a year.
You can also steal ideas from other places. The key is that you have to make it totally your own and not simply mimic what someone else has said.
There's also a reason most great writers have hung out with other creative people. When you get talking to each other, ideas get thrown out and you never know what any of you will come up with.
Let me give you an example:
One of the very first articles I had accepted by an editor came from an idea I "stole" in a sense. Years ago, I'd been part of a Bible study where the pastor had a lot of things to say about Jonah—very few of them good. I have to confess to feeling rather annoyed during the evening, but not completely sure why. Later, I spent some time rereading the book of Jonah and thinking about what had troubled me about the pastor's words. Eventually, I realized that I strongly sympathized with Jonah.
I actually was doing very little writing at that time. Besides having three young sons, I was part of the leadership in a church plant. But I felt so strongly about this one thing that I made time to write an article I called "My Friend, Jonah." It later won a prize in the Alberta Christian Writers Contest. And when I finally began sending pieces out, it was accepted by the first magazine I tried, Confident Living. That gave me a big boost in my desire to do more writing.
Going off-topic, but the irony here is that although I was paid for "My Friend, Jonah" in 1989, the article has never been published. Although Confident Living published a number of other articles I wrote, for some reason, the editor never found the right issue for this one. When the magazine went out of production, they returned my rights to the article.
If you want to read it, here's a link. You'll be one of the first people to read it. 
Writing Exercise:
Look through a few magazines you have. What do you see that interests you, and that could be written from a different perspective?
Check out copyright laws here:
