To pay off debt that has been sent to collections and shows up on your credit report you need to contact those collection agencies and see if they'll remove the negative remarks from your credit report if you pay them off.
Only pay them off though if they agree to remove the negative remarks from your credit report because if they don't report the debt as paid then it won't help your credit rating at all.
Eventually those unpaid debts and remarks will be removed from your credit report after 7 years anyway.
If you do make payment arrangements with the collection agencies to pay off the debt then be sure to always make those payments on time or it can hurt your credit rating worse.
It will take some time however to see your credit score improve after paying off collection agencies and debt that appears on your credit report.
Expect it to take 6 months to a year to see your credit score increase after paying off the debt.