Hi Zeldhoron,
Is your pawn using a CharacterMovementComponent? This is how the character in many of the project templates sends its movement to the server, and it has a lot of built-in functionality to handle movement over a network, such as prediction and correction - so it’s a good place to start if it fits the needs of your project.
For a client to send data to the server, it has to call a Run on Server event (or a Server RPC in C++). The CharacterMovementComponent has implemented RPCs in C++ to handle sending the client’s movement to the server, and for the server to send corrections to the client.
If you’re not using a movement component that supports networking, you’ll probably need to add some custom Run on Server events to send the client’s movement to the server.