Similarly to how the pictures are displayed in the question (see Add Images to Questions), it is possible to include links to websites.
1/ Click onto the 'chain' icon at the top right of the 'Your question' input (next to the 'image' icon). This will produce a pop-up on your screen where you can enter the link you wish to add to your question.
2/ When you have entered this website link you will see it appearing within "(" and ")" inside of the input field.
3/ In front of the link will be [link] - this is what will appear to the respondent - in the example below [link] was replaced by [Click here]. When modifying this make sure that your text is surrounded by the "[" and "]" or else the link won't work correctly.
In the image below, you can see on the left how the link will appear for the respondent and on the right how the input text will look for you when creating and editing questions.