Search the forum, there are a few topics which tell you what to do. Basically you need a program to convert the .dds files and a program like photoshop. Hoppah's files need unlocking as well and there is a topic that tells you how to do that.
Read the last few pages of the topic for that map. Other people have asked the same thing. You just have to put the files in the LA mod v1.8 folder instead of LA Mod v1.7
You can't download LA mod v1.7, but you can download LA mod v1.8 and the map is compatible with LA mod v1.8. To download LA mod v1.8 go to the download center (Click Downloads in the top right corner.)
The winterberg mod on my computer crashes randomly, but other mods like the LA Mod and the England mod don't so I think it will be a problem with the winterberg mod.