Welcome to Android Central! Are you searching for the app on the Play Store app on your phone, or on the Play Store website on your browser? If the app doesn't show up in the Play Store app, then it's not compatible.
Besides, I would avoid that app like the plague anyway. It's one of those bogus "RAM booster" apps that tries to fool you into thinking it's doing something helpful, while in the meantime injecting as many ads as it can (and probably also sending your data to servers in China or other countries). Android phones don't need "RAM booster" apps.