Looking through viewfinder i see dirt & black specks
It depends where the dirt is. Following the light path, look at the rear surface of the lens. A dirty rear lens surface will have the most affect on picture quality or what you see in the viewfinder of any position in the light path. Like all optical cleaning procedures, hold the lens with the rear lens surface facing the ground so gravity will work with you. Start by blowing clean air on it using canned air or a blower such as a Rocket blower or ear syringe. If that is sufficient, do not continue the sequence. This holds true at the conclusion of each step because the more aggressive your cleaning becomes, the more risk there is of damage. If it is still dirty, gently brush it with a sable or camel hair brush. If that is not sufficient, gently wipe it with a dry lens photograph lens tissue (do not use coated tissues) or a microfiber cloth. Finally, as a last resort, dampen a corner of a lens tissue or microfiber cloth (do not put the wet solution directly on the lens) and gently wipe with a circular motion. Finish by wiping with a dry section of the tissue or cloth. Although the front surface of the lens is not as important, repeat the process for the front surface.
If you still see the dirt in the viewfinder, are two possible remaining locations; the bottom surface of the prism located above the mirror or the mirror.
Clean the prism first and avoid cleaning the mirror if possible, or any contact with the mirror. The prism can be cleaned following the sequence outlined above. If that doesn't work, the problem is the mirror.
CAUTION! The mirror is front surfaced and is very susceptible to scratches and other damage unlike a conventional mirror which is rear surfaced with the glass protecting the coating. Aggressive cleaning should be avoided.
Carefully follow step 1 of the lens cleaning procedure (air) and step 2 (brushing) if necessary. As far as the third and fourth steps, I would not use them myself because of the risk of mirror coating damage. It would be better to take your camera to a qualified repairman.
remove the lens and look above the mirror at the bottom of the viewfinder prism. If it is dirty, clean it as you would clean a lens surface. The next place to look is the mirror.
CAUTION! The mirror, unlike the mirror over your bathroom sink, is front surfaced and there is no glass between you and the delicate and easily damaged coating. Hold the camera with the mirror facing down so that gravity will work in your favor. If that does not work, I would stop and take it to a camera repairman because you do not want to risk scratching the surface by using lens tissue or cleaner.