OK,so I downloaded the free diamond edition gog gave out,I downloaded part 1 got to the installer,it then said I need to open a file,I'm not sure which file it wants

there is 2 files...

So I just need to open part 2 when I'm installing part 1?

OK.

You just need to have both parts downloaded to the same folder.
When you run the .exe from part 1, it will open part 2 when it needs it.

Couldn't they have merged the files?

Can't you handle downloading two files?

Of course they could.
But the larger the download, the greater the chance of errors with poor or slow connections, and the more you would have to redownload if a file did get corrupted.

Yeah,just seems a little odd to download files like this

I'm just familiar downloading whole files if I'm honest.

I recomand to Use the Gog Downloader then. After Installing the GoG Downloader you only have to Klick on 1 Link to get the Files und One Link for the Extras . So you have everything together if you Download a Game.

Don't get Dragon Age. It's seven files, eight if you count the hotfix and bonus DLC.

Though if you don't want to worry about multiple files, get GoG Downloader or GoG galaxy, to handle that for you.