You can remove the patch window by either installing the new update, or if the update is a beta version, then by changing your update stream to public. To install the new update, simply follow the instructions on the screen. You may need to ensure 'disable online features' is unticked to do this.

If you do not wish to install a beta update, then you can change your update stream using the following steps:
1) Click on Trainz settings on the launcher screen.
2) Click on the 'install' tab
3) Click on 'Change T:ANE update stream...'
4) Click on next, without changing any details, for install location, and username and password screens.
5) On the 'select patch stream' screen, click on 'change stream' and then select 'TANE - Public Release' in the drop down list, then click 'ok'.
6) Now click on 'done'.

If you need to turn off the 'disable online features' option, then you can do so by following these steps:
1) Click on the 'internet' tab in the Trainz Settings
2) Untick the option for 'disable online features'
3) Close the Trainz settings.