Credit score help

I have a credit score between 540-580. I have about 3-4 collections one of the companies being part of Midland Credit Management. I did poor decision making as soon as I turned 18 now that I’m in my mid 20’s I want to make my credit score. Any help or advise? I can elaborate on some details but I’m running into a conflict where now I’m starting to struggle pretty bad because of it.