1. Select Samba from the Service list
   
2. Select the server/servers you want to modify from the list of Samba servers in the Server Tree
3. Select the "Windows Networking" option from the configuration window. 

   
   

4. Set the Master Browser priority to a low value to force it to become the LMB for the network. 

   

5. Once done click on the create button and the changes will be saved. If you want to create more options for this share you'll need to go to the "view all shares" area and modify them there.
6. After choosing create you'll need to select close to go back to the main screen where you'll need to decide if you want to make more changes to samba, apply all queued changes immediately or schedule them to occur at a later date.

NOTE: Please use this carefully, a misconfigured Samba can cause serious issues while it tries to become a LMB.