People often make assumptions when talking to each other about the gender of the person they are talking to. But those assumptions are not always correct, particularly in EVE where its completely common and accepted for your character not to match your real life gender (for example my main is female but the vast majority of my other characters are male). Addressing someone by the wrong pronoun can be embarrassing for you and potentially upsetting for them - especially if they are transgender or non-binary. Our pronouns are very tied up with our identity, and being repeatedly misgendered can be really damaging. Using someone's preferred pronouns demonstrates respect for them, and telling people what your preferred pronouns are makes it easier for them to avoid making a mistake. It tells people you are not going to make assumptions on their gender and promotes inclusivity.
But also importantly, telling people your preferred pronouns helps to normalise people giving their preferred pronouns. Everyone should feel welcome to share their pronouns, and trans or non-binary people are the only people who display their pronouns it marks them out as different. Personally, as a cisgender person this is a practical way I can help in a small way to remove some of that stigma. Another way is to ensure that I always refer to a person by the pronouns they have given, and correct others politely if they misgender people.
So enough about the 'why', let's explore 'how'.
Discord by default doesn't have a marker for your preferred pronouns. But its super easy to add them into your status so they appear under your name. On desktop click on your profile picture down at the bottom of the channel list:
I would note finally that it is everyone's personal choice whether they wish to give their pronouns. If people don't want to that is absolutely fine. In particular, if someone is struggling with their gender identity they may not be sure what pronouns they associate with, or not ready to tell others. No matter what pronouns you associate with, I love and accept you, and your thoughts are valid.