You can find the internal room ID by looking in the advanced section of the room settings in your Matrix client. It should look like !QMdRCpUIfLwsfjxye6:home.server.
It is highly recommended you create a new user and do not use your own Matrix user's access token as it will allow full access to your account and all the rooms you joined. Instead, create a new user and only invite it to the room that you want to receive the notification in. You can get the access token by running curl -XPOST -d '{"type": "m.login.password", "identifier": {"user": "botusername", "type": "m.id.user"}, "password": "passwordforuser"}' "https://home.server/_matrix/client/r0/login".