This post shows how to connect a shared folder on a Ubuntu machine from another Ubuntu machine on the same network.
You can do it from the Files manager:
Files -> Connect to server -> Open Samba share
Note: The folder being shared should be shared appropriately as well. If you want anyone to access that folder, you can set it as follows:
Share the folder option. This would install Samba service if you are sharing a folder for the first time.
Allow guest access to share folder and be accessible from other Ubuntu machines.