An Aiken file is simply a text file formatted in a way that makes it clear to Moodle what your question is, which possible answers you want to offer, and which answer is correct. For each question, type the question text on a single line, followed by the possible answers each on its own line and prefixed with an upper-case letter and either a period or parenthesis.  After the possible answers, type "ANSWER:" on the next line and indicate which of the possible answers is correct.  For example:

What is the correct answer to this question?
A. Not this one
B. Not this one, either
C. Must be this one!
ANSWER: C

Which LMS has the most quiz import formats?
A) Moodle
B) ATutor
C) Claroline
D) Blackboard
ANSWER: A

A few things to note:

• Your file must be saved as a plain text (.txt) file.  It's also recommended that you save your file using UTF-8 encoding (see the below example from Word -- you're given the choice to save in UTF-8 automatically when you choose to save in plain text format).
• The answer letters (A,B,C, etc.) and the word "ANSWER" must be capitalized
• Remember to add a space after the period or parenthesis following the answer letter, and add a space after the colon following ANSWER
• Separate each question with a blank line

Getting your questions into a quiz is a two-step process.  First, they need to be imported into the quiz's question bank, then added to the quiz itself that the students see.  After creating your quiz, click on its name to go to its landing page.  Then:

1. Click the Question bank tab
2. Choose Import from the drop-down menu

On the screen that appears:

1. In the File format section, choose Aiken format
2. In the General section, click the Import category drop-down menu and you'll see a category named "Default for <Quiz_Name>" where <Quiz_Name> is replaced with the name you gave your quiz.  Choose that category.  Because my quiz is named "Quiz 1," my category is named "Default for Quiz 1."

Finally, use the Choose a file... button to choose your Aiken file, or drag your file into the box.

When finished, click Import.  You'll see a list of the questions imported, which should match the number of questions you'd included in your file.  Click Continue

Go to your quiz's landing page.  Then:

1. Click the Questions tab
2. On the right side of the screen that comes up, click the Add link.  From the menu that appears, choose from question bank

On the next screen, you'll choose which questions you want to import.

1. Open the drop-down menu and you'll see a category named "Default for <Quiz_Name>" where <Quiz_Name> is replaced with the name you gave your quiz.   This is the same category you imported the questions into. Choose that category.
2. Click Apply filters.
3. After you select a category, the questions you imported will appear.  Choose which you want to import with the checkboxes.  Click the topmost checkbox to select all the questions.
4. Click Add selected questions to the quiz when finished

Once the questions have been added, you can order the questions, add page breaks, shuffling, etc., as with any other quiz.