Arthritus. Boney growths everywhere. Pain and weakness in neck, upper back and right arm. Emg shows nerve damage at C5 (already stenosis). What now?

Need MRI of neck. You need an MRI of your neck to locate the area of spinal stenosis. You should go see an orthopedic spine surgeon after the MRI and will likely need epidural steroid injections in your cervical spine. If the injections do not work, likely you would need cervical neck surgery.
See details. The options are limited in this situation. If you arm is truly weak then cervical spine surgery may be the only option. Have the issue evaluated including MRI and emgs if they have not been done already. One can try physical therapy or targeted injections bur true arm weakness usually means surgery.