Gabi,
This sounds like an excellent little project! Great way to get your feet wet in Unreal.
First off, have you attempted anything yet? Do you have any familiarity with Blueprints or C++ coding? I personally prefer working in C++, but this sounds like something that can be done very quickly in Blueprints if you’re code-shy.
If it were me approaching this, I would first set up one collision box at the base of the ladder and one at the top. That way, you will be able to detect when the player runs in to the ladder’s space, as well as if the player is going up the ladder (they’re overlapping with base collider) or going down (overlapping with the top collider.)
From there, we could go a few different ways. One way would be to change the controls from X & Y horizontal movement to Z & Y vertical movement, like Minecraft does. Another approach would be to turn off player input and simply start moving the player upwards until they reach the top, then turn player input back on. A VERY simple solution could be to teleport the player from the base of the ladder to the top of the ladder, possibly with a fade-in / fade-out transition if you really wanted to get fancy.
So really, the solution to your problem depends on how much coding/blueprinting you’re willing to do, balanced against the effect you’re wanting.