How to fill the front suspension on a ktm exc 2001

What about air shocks? Are they done the same way?

If you get the sevice manual or contact a dealer to get the correct oil amount for your bike, they need to know the model and year, you have to have the forks off the bike. take the fork caps off, take the springs out compress the upper fork tube all the way and add the specified oil. if they also give you the measured amount from the top that's the best way to get both fork oil levels exact. there is a special tool that you set the oil level in millimeters and it sucks out the oil to the right level, but before you do that step after adding the oil always pull and push on the cartage rod several times to remove air from the cartage tube. you will hear the air coming out and you will feel the changes in the cartage rod as the cartage tube fills up with oil and the air is removed.
something i'm confussed on though is if you replaced a seal you would have had to brake down the fork to replace it. you would have poored the oil into a container, cleaned all the internal parts,and used a fork seal driver to install the new seal. part of your question asks where do i put the oil in? thats in the open end of the fork after you have taken off the fork cap. It sounds to me like you only replaced the dust seal on one fork. that is not going to fix your leaking fork. you need to replace the oil seal thats pressed inside of the top fork tube.