As MattorS said, you have only been playing on the server for a day so far. We recommend at least 2 weeks before applying for staff to gather knowledge of the server and our rules.
Give two examples of unacceptable KOS and their scenarios:
1. A person shouting KOS "Jeff" and then Jeff gets shot, that is unacceptable.
2. Killing someone for having a T weapon on them without asking him about it.
Reason 1 is completely valid. If player x was to KOS player y, it would be valid/acceptable.
For the second one also, if a player has not said anything about having a t weapon picked up from a T, you don’t need to question them before killing them for it.