How to increase Website DA (domain authority)?

Hi Friends......How to increase Website DA (domain authority)? my website domain authority is now very low almost 7 so what i do for increase my domain authority..please suggest some solution thanks...

6 Practical Steps on How to Improve your Domain Authority

-Work on Your Off-Page SEO
-On-Page SEO Optimization
-Work on Your Technical SEO
-Make Sure Your Website is Mobile Friendly
-Improve Your Page Speed
-Increase Your Social Signals

@sophia, by implementing these steps, what's the current DA & previous one? how much time does it take?

The current DA is 7 and how old the website (domain) is? Age also affects the DA! SEO link building will also help to increase DA.