Sharing folders with xubuntu out of the box requires adding a few packages and using the command line.
Here are the steps:
sudo apt install system-config-samba gksu
Then from the command line
Then you will add the folder you want to share the the dialog and choose the user(s) that will be allowed to access the share.
The share you created will not be available on the network. Typically this will be displayed undre Windows Network, then you will see your computer name in the list.
On the remote machine you will be prompted for a username and password once you try to access the share. Use the same account information that you used on the machine on which you created the share.