"Open.Country-CODEX.part1.rar" refers to the first part of a split RAR archive, typically used to distribute large files, such as a PC game cracked by the scene group CODEX.
Use software like WinRAR or 7-Zip to right-click on the part1 file and choose "Extract Here". Open.Country-CODEX.part1.rar
Once extracted, the resulting files usually contain an ISO image or a setup folder. You will likely find a setup.exe or equivalent file to install the game. typically used to distribute large files