In order to see what you are doing in your darkroom you need some form of lighting which is not going to affect ( fog ) your photographic paper. Film must be handled in complete darkness. Colour film requires a different colour safelighting and is not covered here although the same rules apply.
Black and white printing paper is relatively insensitive to red light so safelighting usually takes the form of a lamp covered with a coloured filter. The colour will depend on the paper you are using and will be marked on the papers packaging. It will probably be amber/orange or deep red. The deep red filter supplied with many safelights will cover both.
So far so good. Unfortunately you can't just stick a 200 watt red light in your darkroom and wonder what all this " dark" business is about. Because the paper is "relatively" insensitive to red light and because the red dyes in the safelight filter are not 100% efficient at filtering the light you can still fog your paper.
  • Your safelight is to bright.
  • Your safelight is to close to the paper.
  • You expose your paper to "safelighting" for to long.
or, as mentioned above, your safelight is the wrong colour .

Check your paper pack for safelight colour and check your safelight handbook for a guide on how close it can be. At least 3 feet/1 metre is a good starting point for small safelights. When you have your safelight or lights set up you will have to carry out a test to check the level of safelight fogging present.

Next safelight testing.