First, get your credit reports (free of charge from the site below) and review them for accuracy.
https://www.annualcreditreport.com/index.action
Sign up for Turbo (for free credit scores and other pertinent information).
See https://turbo.intuit.com/
Read the information at the sites linked to below for tips on improving your score.
https://www.experian.com/blogs/ask-experian/credit-education/improving-credit/improve-credit-score/
https://www.bankrate.com/finance/debt/7-simple-ways-improve-credit-score-1.aspx
