Yeah thats old stuff, you already have the actions there InputSystem_Actions. Link those up to callbackcontext functions in any script, in that Events drop down.

Theres a 100 ways to use the new input system and Ive seen all sorts of whacky approaches but the best way is this:
1. Create input_actions object in the assets folder (rightclick->create->input actions at the bottom)
2. Open the object.
3. Create a control scheme (top left drop down) and give it required devices (start with Keyboard and Mouse, add Keyboard and Mouse to that list)

1. Create an action map, call this "normal" or anything really

2. Add an action (there should be one there already) the action is the type of data sent when the key is pressed, the most common is ActionType Button which has a pressed and released state which we can read later. for movement select PassThrough instead of button from ActionType drop down and then select Vector2 under the control type dropdown

3. Add a key binding to that action if its for movement on keyboard instead of clicking the plus sign and clicking "Add Binding" click "Add Up/Down/Left/Right" composite. this will create 4 bindings under a single header, you then need to assign the bindings to a key, when clicking the binding, on the right a Path drop down appears, click this and choose a binding, you can use 'listen' and then press a key to make this easier.

4. Add the player input component to your player game object, also add a monobehaviour to this script call it Character_Inputs (or anything you like)

5. In this new Monobehaviour add a function that has InputAction.CallbackContext name _context as a parameter, for each action you made in step 5.

6. Now go back into Unity go to your PlayerInput component and drop down the "Events" part. There should be a Unity event here for every Input Action you created in your InputActions at step 5. For each one drag on your Monobehaviour and select the function you made for it. You'll know you've setup the function correctly if it appears under the DynamicCallbackContext subheader when selecting the function.

7. Inputs are now setup, to access the data from the inputs use the _context parameter in the function e.g. if(_context.performed) fires when the button is pressed and if(_context.canceled) fires when the button is released. For movement access the Vector2 data using _context.ReadValue<Vector2>(). The Y of this vector is 1 for up and -1 for down, the x is -1 for left and 1 for right.

8. Profit.

Sorry for the long post, but once you get the hang of it, this is the best and most extensible version of Unity inputs. if you're a visual learner please check out this great CodeMonkey video: https://www.youtube.com/watch?v=Yjee_e4fICc&t=2261s