first thing is buy some cheap oil and a few oilfilters. drain as much out as possible on each change, refill with cheap oil and change filter, two quarts will be enough per change to flush with. some people reuse the filters, its fine but need to be cleaned good before reusing them. let the bike at least get warm before draining. drain and replace filter. repeat this untill no water is visible. Depending on how much water got in will depend on the number of changes needed.