Can I record Firestick

The input to the EzRecorder has to be an HDMI signal (the format of the signal going into most TVs these days). If you can output the content of your Firestick as HDMI, the recorder can record it. If the content of the Firestick has HDCP copy protection, you have to have a splitter for you to record.

What is HDCP?

https://www.digitalconnection.com/faq/hdtv_12.asp