I do not seem to be able to paste an image from mac i photo to QGIS print composer. When i click on add image I get a blank box with no photo.
Also when I click to add a label I do not seem to be able to change the text in the label box.
You set all the options and properties for each of the map composer elements in the right hand panel "Item Properties". Here you can enter any text into the label (and change font, etc), and regarding images, there's a button in the right hand Item properties panel next to "Load another" to search for any image file on your computer.
If, for some reason the Item Properties panel doesn't appear, then right click anywhere in the toolbar, and check "Item properties" so it will appear. The contents of this panel change for each map composer item that is currently selected.
You can have a look at the current QGIS manual here for more detailed explanantions.