Bethesda has launched Fallout 4 and they have done a great job with the game. However there is one thing that they failed to make all that clear and it is setting up the supply lines that came with the Sanctuary Building quest so you can share your resources.
Bethesda did give some instructions on the setting up of the supply lines in Fallout 4 but it seems that there are some people that have been having issues in setting up the supply lines. So if you are among these people you can follow our easier guide.
One of the first things that you need to do is invest in Charisma Tree > Local Leader and this means that you will then be able to send out caravans to and from settlements. Once you have done this you should then be able to share all the resources collected in the Workshop with the other settlements.
When you go into the Workshop mode you can choose a settler and then hang around until it turns into a provisioner. You can then share the resources that you collected in the game.