L2TP to specific port on switch?

Looking at Mangle Rules in IPv4 Firewall, the Chain has 5 options:

  • forward
  • input
  • output
  • postrouting
  • prerouting

The wiki about Mangle
https://wiki.mikrotik.com/wiki/Manual:IP/Firewall/Mangle
does not explain what exactly it is that I want.

Would you be able to help with CLI comand pls?
My local IP that I want to route via the L2TP connection is 192.168.168.68
The L2TP connection is called l2tp-out-UK-vpn

Thanx in advance.