D2Damnation runs off of a 1.10 server. To make sure that you recieve the full gameplay potention from D2 Damnation make sure that you do the following..

1) Revert from 1.11, 1.10, or another patch using a 1.09 reverter. Which can be found here

2) Make sure you install a v1.10 blizzard patch to update your mpq files to make sure they are clean. 1.10 Patch here

3) Get the latest D2Damnation Patch and extract ALL files to your d2 directory and overwrite all. Patch is here

4) Get gateway editor and create a new gateway under the Diablo 2/Diablo 2 Lord of Destruction tab. and enter the following information.
Server Name: DamNation
Time Zone: -6
Server IP: Damnation.no-ip.info

Gateway editor can be found here

Then all you need to do is create an account by applying in the forums, the application is located herethere is usually someone on who can help and if you have any questions or concerns you can report it to the forums here