1. Using OpenIV, extract the contents of the folder "x64" to: \Grand Theft Auto V\mods\update\x64\dlcpacks

2. Using OpenIV, go to: \Grand Theft Auto V\update\update.rpf\common\data  and extract the "dlclist.xml" in some folder of your choice.

3. Add the following line: <Item>dlcpacks:\opelastra\</Item>	

Done! :)