if you are replacing the one that goes into the tank from the carb, I found it helpful to cut the first couple inches of the fuel line in half (so it makes sort of a point).  It makes it easier to feed that part through the hole in the tank.  Once that is inserted you should be able to get ahold of it with a needle nose to pull the fuel line through then just cut that piece off and add the filter to the end.
                 Bill
                
 August 2004