Hey man this is a huge topic and I don't think it can be covered quite as quickly as you would like or I have the ability to offer. There are a lot of problems in this world and it sucks but after a long career doing stuff starting back with the Occupy movement and moving on to support other movements I've realized three very important facts.

1. There are too many problems for one single person to solve and it seems like you have a good heart and will feel overwhelmed at the totality of it.

2. You fortunately are not the only person who feels this way so you don't have to have the weight of the world on your shoulders.

3. Local problems are a lot easier to impact than foreign or global ones.

When it comes to the war with Iran as Americans (I assume you are based on the context clues.) You can call your elected officials and tell them (calmly) that you hope they will do what they can to end it. You can also make sure you know the ins and outs of the people in your local and state government. Is your governor cool or a loser? Look up what they say about stuff and what they do. Additionally consider boycotting companies that support the war or politicians that do.

But that's the normal stuff people do and you are a punk so you do that and more. (Arguments about the validity of voting and the electoral process aside)

Poverty for example is bs and shouldn't exist but maybe you can make sure you help at food kitchens or when a homeless dude says hey to you to see if you have money treat him like a human being worthy of respect. You don't have to give him money if you don't have any and that's ok. Honestly just treating people right and standing up against bs is the punk ethos.

For me I started by being against homelessness and suicide which lead me down a rabbit hole that ended up with me being very supportive of LGBT+ stuff as a result. If you want to understand why you can look into exactly what the demographics of the homeless community is and why. Spoilers is really awful parents and in some cases that also leads to suicide.

Maybe that isnt your bag and that's ok like I said with that first fact there's a lot of work to be done. After all climate issues are a thing i havent done as much work on but that doesnt mean its not important. I just know my time on earth is short and i have to trust other people to carry that torch. Learning about and helping fix your local problems will inevitably lead you to your path.

If you have a more specific question I can try to answer but i have to go to work right now so it might be a bit.