How to increase domain Authority ?

Many things have to be done.
Here are some ways you can increase your site's DA:
Acquire High-Quality Backlinks from Authority Sites.
Create Killer Content That's Link Worthy.
Audit Your Site and Remove Bad Links.
Optimize Your Website Structure and User Experience.
Improve Your Internal Links

Domain authority is nothing but a parameter to calculate your domain's search performance according to Google search results. In other words, A Domain Authority is a metric to show the number of root domains that link to different pages on your site, rather than all links pointing to your homepage. So if your site has a number of links from different pages, it's considered to rank better than other sites that link to their homepage. Domain authority measured in the 0-100 points scale.

To increase your website's domain authority, start working on your SEO activities, including On-page SEO, Off-page SEO, and Technical SEO. Optimize your website, remove spammy links, and start building backlinks daily by performing a list of off-page activities.

Link juice is an SEO term that refers to the value of a page passed to other webpages. It gives a vote of confidence to the search engine, as more links pointing towards a page show that it’s trustworthy. All of this adds up to boosting domain authority.

Increase the number of linking domains

To increase your website's domain authority, start working on your SEO activities, including On-page SEO, Off-page SEO, and Technical SEO. Optimize your website, remove spammy links, and start building backlinks daily by performing a list of off-page activities.

Good Content is Increase domain Authority.

Write content for your site that people want to link to, try and include user generated content on your site.

work on On Page Seo and and Make Good qulaity Backlinks.

Start SEO for that website

To increase your website's domain authority, start working on your SEO activities, including On-page SEO, Off-page SEO, and Technical SEO. Optimize your website, remove spammy links, and start building backlinks daily by performing a list of off-page activities.

Start SEO for that website and provide it powerful backlinks.

Work on Your Technical SEO.

Increase the number of backlinks on different domains.

Work on Your Technical SEO.

Work on Your Technical SEO.

Create Killer Content That's Link Worthy. ...
Audit Your Site and Remove Bad Links. ...
Optimize Your Website Structure and User Experience.

Increase the number of linking domains

Work on Your Technical SEO.

These are the steps to follow to practically increase 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.
Be Patient.