Navigate to the Tests option within the Tests section. Click on the scheduled test you want to delete (scheduled tests are displayed in a white rectangle). 

You will be transferred to a summary page of all the settings for your test you specified earlier. You can edit all of the features here.

If you scroll down to the bottom of the page, you will see the option to delete your test. 

Heads up: the deletion cannot be undone afterwards so make sure you have the important details saved somewhere. You might want to use the same meta description for example in another test so we recommend to copy all useful information before you press delete.