how can I enter password on wifi network for apple tv version 3 model A1427?

Normally, you would be asked to for a new network, and enter it using the remote.

1. Try the steps as mentioned in: If your Apple TV can't connect to Wi-Fi - Apple Support
2. Try the ‘Other…’ option instead of selecting a listed discovered network. Especially if the password has been changed.
3. For Apple TV (4th generation or earlier), verify that the router or access point isn’t set to use WPA3, as only device models from ~2018 or later support that. Instead use ‘WPA2/WPA3 Transitional’. Some users report having to set ‘WPA2’-only first, in order to make it work.