Bad credit

I had posted a couple weeks ago about my struggles of being a teen mom and how I let that destroy my credit score. I never really knew what "credit" was. Like I mentioned before by the age of 16 I became a mom of TWO kids and well because of it I got myself in a very messy situation with bills and not being able to pay them on time. Now that I'm older (25 my kids are 9 & 8 years old ☺️ ) I see how important a good credit score is. I'm determined to fix my credit score now that I have a good paying job and a supportive fiancé. Where do I begin ? I'm actually looking into getting professional help with my credit. Has anybody ever fixed their credit with professional help ? How is it that they help you ? Any advice or insight I'll highly appreciate it 💓💓