How to clean the electronic bit on a DSLR?

Sorry don't know what its called but I've just noticed that on all my photo's I have two very slightly dark spots… Like a dried water spot… It happen's with all the lens's, so it must be IN the camera. I only notice it when I shoot clouds or other light backgrounds.
My camera is a Nikon D50

I would just send it back to Nikon and let them troubleshoot it.

That is dust on your sensor.

To remove it you need a blower like the Rocket blower.

* using the blower, puff some air into the chamber behind your lens in the camera. This will remove any dust that has not reached your sensor
* lock the camera mirror out of the way so you can see your shutter.
* open the shutter using the bulb setting.
* with the camera facing down, use a few gentle puffs from the blower.
* re-attach the lens and take some shots of sky.
* view the sky shot on your computer and look for other dust on the sensor. If there's some, use the blower to puff any remaining dust on the sensor
* do NOT touch the sensor

In the future, so NOT change lenses in dusty areas or in the wind.

From time to time, blow any dust that accumulates in the chamber behind your lens where the mirror and shutter reside

This may be a repair best left to a professional.

Fhotoace hit the nail on the head, it's dust on your sensor. Use an air blower to remove it or bring it to a proper camera shop to get cleaned (this costs money) or you can send it to Canon for cleaning (may also cost money).

A bit of advice for keeping out dust:
Try not to change lenses much. Try to remove the lens from the camera as little as possible actually.
Avoid changing lenses in the wind or in dusty areas.
If you have to change lenses, hold the camera so the LCD is facing directly upwards. OR, hold it so the lens mount is resting against your body - this prevents wind from blowing dust in there.

I use several camera bodies to avoid changing lenses much when I'm shooting. This isn't an option for everyone but if you're thinking about getting serious about photography then investing in a second body is a good idea.
I shoot with 2 bodies typically, but I shoot sports with 3 bodies, sometimes 4. Each body has a different lens so I'm ready for all occasions and don't have to change lenses much.