Just bought a 79 R65, hasn’t run in a decade
Please do not simply change the oil, pour fuel into it, connect a battery and see what happens.
What you need to do is "recommission" the machine which means systematically checking/cleaning all of the major components prior to the first attempted start.
There is a copy of the factory repair manual available online, my recommendation is that you ignore it as the problem with the factory text is that it presupposes that you have attended BMW specific training and have all of the Matra special tools in your cabinet.
You are far, far better off buying a Clymer or Haynes manual - these regularly appear on eBay for little money.
Your other major resource that you are going to need is Snowbums occasionally soporific web pages
See
http://bmwmotorcycletech.info/technical-articles-list.htmLastly, welcome. The natives are (mostly) friendly and we just love photographs. In case that isn't an obvious enough hint - post photographs..