how do I add a device to my device list?

Apple TVs are never added to the device list. Note my comment above. Having a device added to this list serves to restrict what you can do, there is no tangible benefit.

tt2

i purchased iPhone 7s from costco

my old iPhone 6s went for a swim saturaday a drown ,

so how to and this new device?

Which devices list?

Authorization vs. association

Up to 5 computers can be simultaneously authorized for each Apple ID. There is no direct record of which machines are authorized. It is up to you to keep track. iPods & iOS devices are limited to DRM protected content from up to 5 different accounts. There is no limit to the number of devices that you can load up with content using iTunes. You can deauthorize computers that you no longer wish to use to access protected content so that you can authorize others. You either do this on the specific machine or deauthorize all and then reauthorize as needed. Having used deathorize all you cannot use it again for a year, though Apple Support may be able to perform a reset if you can explain why you need to use the feature again before it becomes available to you.

HT201251: Authorize your computer in iTunes - Apple Support

A mix of up to 10 computers and iOS devices (no more than 5 computers) can be associated with your Apple ID for iTunes Match/Apple Music or automatic downloads of past purchases. There is a 90 day limit before a computer or device can be switched to another ID or the association removed. The list of associated devices is the one you can see within your account details in iTunes. You associate a device or computer by using certain features, typically downloading past purchases. You don't necessarily need to associate a computer or device with your Apple ID to use it with your content.

HT204074: View and remove associated devices in iTunes - Apple Support

You can happily remove any and all associations that are not within the 90 day limit. Those that you actually use will be recreated as when you make use of a service that triggers association.

tt2

why can't i add my mac to devices

I want to add my apple tv to my device list

I want to add my MacBookPro to my device list.

I want to add my MacBookPro to the devices list. There was no "edit" so how do I do it?

sign into iCloud on the device.

If that's not what you're looking to do, then please provide more details, as we're not psychic.

See HT204074: View and remove associated devices in iTunes - Apple Support. Certain activities will cause a device or computer to become associated with your account. It isn't possible to associate an iPod classic. You don't necessarily need to associate each of your devices.

tt2

my ipad is disabled and im trying to add it to my device list so i can unlock it