Available in Win 8 and higher.

1. Press Win+R on your keyboard.

2. Enter mstsc.exe and press OK

3. Enter IP\Name of PC and User name

4. Check "Allow me to save credentials"

5. Press "Save as" and save it in PolywallContent folder for example.

6. Open shortcut with notepad

7. Screen mode id should be setted to 1

8. Enter "smart sizing:i:1" at the end of the list.

9. Save changes and close the file.

10. Open Polywall Designer

11. Create application source

12. Enter name of the source

13. In "Path: field enter "C:\Windows\Sysnative\mstsc.exe" "C:\*Path to RDP file*\NAME.rdp"

14. Drag and drop the source.

15. During first boot check "don't ask me again" in each window.

16. Enter credentials. "Remember me" should be checked.

P.S. Due to winposstr:s:0,1 parameter inside of rdp file when you drag and drop it, source  will appear in the left upper corner of the videowall. Just move the source inside Live section and it will swap size and location. Or you can setup start position of the file by yourself - https://social.technet.microsoft.com/wiki/contents/articles/665.how-to-set-the-monitor-for-a-remote-desktop-session-in-a-multi-monitor-setup.aspx