i'm advertising some places to rent, and i need to put some photo's on the thread,
any advice how to do this ?

you need to upload your pics onto a hosting site, I use photobucket.com but there are others.
Then just add the link to your post.

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Upload your images to a hosting service, like photobucket or imageshack (google for them), and then put the link back to your images on your for sale/rent thread.

Easy as the proverbial pie.