Attach Spawned Actor_BP to a Spline_BP within the Game

I have a Character_BP which when located into the Map with the Spline_BP prior to game start, I am able to attach the Character_BP to the Spline_BP by way of BP_referencing and then selecting the patrol path in the details panel.

Although I am unable to attach a Spawned Character_BP to the same Spline (Already placed in the Map) can some one please provide some insight to how I should go about this?

Thank you.