on-campus jobs for freshmen

i’m thinking about getting an on-campus job as a freshman and i saw that desk jobs are really good for being able to study while also getting job experience and being paid. i’m wondering a few things though:

- what’s it like to be a desk assistant and are they typically understanding if you have classes?
- how competitive is it to get such a job as a freshman?
- when should i apply so that i could start sometime during my freshman year?

thank you for responding in advance!