Bushnell has an excellent archive for discontinued scopes, which the "EG" model likely is.
Your manual covers "Sighting In." Here is the condensed version. bushnell 3-9x40eg manual
While the official tells you to "keep lenses clean," a long-term owner should follow this schedule: Bushnell has an excellent archive for discontinued scopes,
A common question for owners of this model is: "Why is the reticle blurry?" bushnell 3-9x40eg manual