Jayeyy - Do you have a router?
Even with a router, I have my IP addresses set manually. You already have done that to direct connect the two units to your PC. You may also be able to use just a switch without a router. SPHardy would know more about that than I would. In mine I have an older router with 10/100 ports so to get the benefit of a gigabit connection, I have a Netgear GS108 switch connected to the router, with my NAS units (3) and my wired desktop connected to the switch.
As for the settings - if you are going to pull the data from the Duo to the Pro, my NAS3 settings are more appropriate as I pull the data from NAS2 to NAS3. (I am obviously very creative with my naming
On the source NAS (Duo) you need to give permissions to the other NAS to read/write to the share. Assume that you are pulling from a share named data, you need to first enable rsync by clicking on the rsync image for the share, then in the next box that opens, enable read/write and then in the box for share access restrictions, check the box for host allowed access, and list the IP address of the target unit. (In my case I have the last part of the IP sequential for my three NAS units, 201 for NAS1, 202, and 203 for the other two. It makes it easier to keep track.)
Since you are pulling you do not set up a backup job on the source unit. (my NAS2 has no backup jobs).
On the target unit, you need to set up the backup job. For example my backup Job001 (on NAS3) in the box "Select backup source" is set for Remote: Rsync server. In the host box is the IP address of my NAS2 (nothing else, just the IP address). Then in the path is the name of the share I am backing up. If you are limiting the backup to a folder, you then then add a / and the folder name. In my case, backup Job001 backs up my finance share so the word finance is in the path box with no folders listed, as I want to backup the entire share.
Then in the box "Select backup destination" list the share name by clicking on the down arrow and then select "Share: sharename". If you want to back up to a particular folder, I believe you would put the path within the share in the path by using forward slashes "/folder/subfolder" although I have never done that. The shares on my backup NAS mirror the shares on my source unit.
Remember - the NAS is not a backup plan.
Backup = Good, No Backup = Bad