To turn a component over and place it on the back of the board, just select it and press the <F> key (the default shortcut for the Flip command). Alternatively, you could right-click and choose Flip from the context menu, or open the component properties and tick the Mirrored checkbox on the Component tab.

When you move a component to the other side of the board, the program looks for layers with the same layer type but on the reverse side of the board.  If this is not present, the information will remain on the original layer but will still be reversed.  So, for instance, if a bottom silk screen layer had not been defined, or used a different layer type from the top, the silk screen would not move, just be reversed.  If this is an oversight, flip the component back, correct the error, then flip it again.