Yes, you can have an ATOM and an AP305C in the same XIQ instance, you'll just need to make sure your Pilot XIQ instance has the licenses to support two devices. If you do not currently have the license to support the new device, you'll want to reach out to your Extreme account manager to purchase an additional license. Alternatively, we have a free version of XIQ called Connect, you could always
register for a connect instance and then add your devices without any licenses.
With either a Pilot or Connect instance,
this guide reviews how to add devices to your inventory. You can check what license you have by logging in to XIQ> Click on the silhouette icon next to your name in the top right hand corner> Global settings> License Management (Left hand side menu, under the Administration header).
Hope that helps!