How can I call a phone number on click?

You can use a link for this purpose similarly as you see here, that the link should be:

tel:+4733378901

with your phone number.

If you are using for example a Heading layer or Button layer, you can insert this into its Link option.

In the Text layer you can insert html code too, so you could write something like this in it:

Call me on <a href="tel:+4733378901">+47 333 78 901</a>

to have a href link there.