When you create a new test, you might want to clone an old test or copy a few questions from it. Here is how to do that.
Create a new test as usual.
Head over to the Questions section at the top of the page.
Once there, click the New Question dropdown and select Add From Existing Test.
Select any of your existing tests from the available list on the left side and choose the questions you want to add to your new test.
For each question, click Pick Task to add it to the current test.
Close the library after you have added all the questions you need.
Note: You might want to change the Time Limit of the test as you see fit after this.