In order to import questions from another quiz to the current quiz, select the item Import quiz from the File menu, then select the item "From quiz file (XQZ or QZ).."
A dialog window will appear, and you can select the file name (with file extension .XQZ or .QZ) of the quiz to be imported. Then, a new dialog window will appear, as shown in figure below:
In this dialog window you can choose whether to import all the questions or only the selected questions, and the entry position of imported questions: at the head of current quiz, at the end or in the current position.
In order to select a question, click on the first column. To select more than one question, use the key Ctrl and Shift when you press the left mouse button.