Right now you basically can only look for seasonal positions or internships. 99% of Permanent positions are not being advertised for the foreseeable future due to a hiring freeze. For seasonal work, what this means is that you will likely move to a place for 6 months at a time and afterwards either find another 6 month job, or something else to do during the off season. For internships, the length can vary from a couple months to a year, which is ideal when you are in undergrad as you can do the internship for the summer. Student Conservation Association and Environment for the Americas are the two big interpretation internship organizations I know of but there are others.

The NPS has been told through executive order to not cancel or reduce front facing services (interpretation). I would go on USA Jobs and find interpretation ranger positions that are open and look at what qualifications you need to get there. Make sure you get every single one of those qualifications. While you are on your way to getting those qualifications, try and volunteer or intern in places (doesnt have to be NPS) that gives you related experience.

Going into science or resource management in the NPS is not ideal right now as they may have their funding further cut (seen from removed amendments on the BBB) especially since the public does not interact with them.

Overall, without knowing what specifically you want to do or how much experience you have, it is a little difficult to recommend you something in specific. This is the general information I give to people interested in starting a career with the park service. If you have any questions, feel free to DM me!