If you look at your seal ,you'll have the metal face and the rear open.The plastic sleave is to install it,don't remove it or touch the seal with your fingers.
Now the steel part of the seal will always face out and the metal install ring ( they are ok to use ) the plastic sleave will slide over the crank and will push out the front once the seal has meet the crank.The metal ring tool will be flush with the cover when it's all the way in.
The front and rear seal are installed the same way.
The cheaper seals won't come with the metal ring or the plastic sleave.
I hope that helps ,hard to say what I just do without thinking about it.
One other thing to do ,when the old seal is out look a the sealing surface .I have seen some that the seal was so bad we had to use a ready sleave to fix the crank .
The seals don't have to be Cummins to be good,I know there will be somone that won't buy anything but Cummins parts.
Crewcab59