Connecting Microsoft Excel with Stratosphere is incredibly simple and won't take more than a few seconds to set up.
First, make sure you have the Excel add-in downloaded. You should have a link in your activation email, but if you don't want to dig through your email to find it, you can download the installer again right here.
Once you have the add-in installed, you should see a new tab at the top of your Excel toolbar labeled "Stratosphere." To connect your Stratosphere account, simply click this tab and then click the button that says "Sign in." Then, you just type in your email and password, and you're all set.
If you're having trouble with this step, the most likely culprit is that the Stratosphere tab is not appearing in your Excel toolbar. To solve this issue go to File > Options > Add-ins > Select COM Add-ins in the dropdown menu at the bottom > Press "Go" > Click the box next to "Stratosphere" > Press OK