Pry damaged fascia board off of house. Cut off the damaged end of the old fascia. Cut a new board to match the part that was cut off. Join the old and new fascia boards and then nail the rest of the new fascia board into the roof rafters.
Depending on the condition, you may be able to repair it with caulking, wood filler, and a fresh coat of paint. If it's in pretty bad condition, it is usually best to simply replace them.
Well if you want to repair the board, first of all seek the area of damages. Then acquire some wood to brace the areas. If their is other damage, then glaze the board.
The first step that you need to do to repair a fascia board is remove the gutter to ger to the board, and the removed the damaged are and replace with new wood.
Remove damaged fascia board. Take note of all measurements and cut angles. Purchase new fascia board with same thickness. Cut to noted measurements. Install.