Move the pack to the "Selected" column in your game menu.
If the goal is to use Xray for retro single-player gameplay, it is recommended to use the "Xray Mod by AmbientOcclusion" archived on legitimate mod sites, ensuring virus scans are performed. If the goal is usage on servers, it is unlikely to be effective due to server-side anti-cheat protections developed in the decade since 1.5.2's release. minecraft 152 xray work
So, does in 2024/2025? Yes, but only in legacy single-player or badly configured vanilla 1.5.2 servers. It no longer works on modern Realms, Hypixel, or any server updated past 1.8. Move the pack to the "Selected" column in your game menu