Unwritable Local Folders

I just installed a local version of wordpress to develop a ecommerce site using wp-ecommerce. That is all well and good. The issue is that when I try to upload images I get these errors:

The following directories are not writable:

* /Users/VINTOM/Sites/wordpress//Users/VINTOM/Sites/wordpress/wp-content/uploads/wpsc/downloadables/
* /Users/VINTOM/Sites/wordpress//Users/VINTOM/Sites/wordpress/wp-content/uploads/wpsc/previews/
* /Users/VINTOM/Sites/wordpress//Users/VINTOM/Sites/wordpress/wp-content/uploads/wpsc/product_images/
* /Users/VINTOM/Sites/wordpress//Users/VINTOM/Sites/wordpress/wp-content/uploads/wpsc/product_images/thumbnails/
* /Users/VINTOM/Sites/wordpress//Users/VINTOM/Sites/wordpress/wp-content/uploads/wpsc/category_images/

You won’t be able to upload any images or files here. You will need to change the permissions on these directories to make them writable.

Any clue how I make thise writable? I changed the permission on my mac folder to allow read/write…

Thanks for the help.