I want to tie another line into my septic tank. Can I tie it into the line before the tank or does it have to go into the tank? HOW IS THE BEST WAY TO DO IT?

It will be easier to tie into the existing line than to cut a new inlet into the concrete tank. Do not make a T connection, use a Y facing the tank so the flow will not have a chance to back up the original line. What are you adding and do you know the size of your existing tank. It is important to not overload a tank and its field. An overloaded tank will allow soilds into the field and you are totally messed up once that happens.