An attempt is an effort to complete a stage within a challenge. There are 3 possible stages: 

• Select Vulnerability Category
• Locate Vulnerability 
• Identify Solution

Select Vulnerability Category 

Select a vulnerability category and press 'Submit'

Locate Vulnerability

Select the Vulnerable code blocks and press 'Submit'

Identify Solution

Click 'View Solutions' 

Select one of the solutions from the drop-down menu on the right-hand side and click 'Accept'

Hot Tip: You can compare two solutions by using the drop-down menu to the left-hand side. Refer to the screenshot below