Using brushes???

I know this is probably the dumbest question ever ... but I just can't figure it out. I looked at the FAQs and older posts, but still can't figure it out! :-(

I use Photoshop Elements 6.

I downloaded brushes and also managed to install them. However, when trying to use them the outcome is like this:

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The brushes mask exactly the wrong areas ... Know what I mean?

What did I do wrong? Can anybody help pleeeeeeez!