Activate new Gateway modem

I was sent a new Gateway modem. I had gotten several emails telling me I needed it to get increased speeds. Emails said step by step instructions would be included. I did not receive any instructions. Instead an email followed saying I needed to download Xfinity app. My phone is not comptable, so that is not an option. Is there any other way to activate the modem? If not, I will return it and keep what I have. Would not have gotten it if I emails had not implied it was easy setup. Thanks for any help!