First, click the jigsaw button in the top right corner of the screen;
There, click "Manage Extensions":
In the window that opens, toggle the "Developer Mode" in the top right corner:
Now, click the "Update" button in the top-left area of the screen and wait a little:
If you have been directed to this page by a support team, they will tell you which version to expect. You can find it here:
In this example, the version is "1.7.12".