Here are 5 approaches:
1: Examine Your Competition
First, you can examine what your competition is doing and get ideas from that: https://blog.monitorbacklinks.com/seo/analysing-competitors-seo-replicate-best-backlinks/ (You can refer to this post to identify what counts as a good link).
For example, are they getting their links from directories? Content that they've created? Guest blog posts? Most likely, what has worked for them will also work for you.
If you find that your competitors don't have many links, then think more broadly about what counts as a competitor for you (for example, thinking regionally instead of locally). One way to do this is to consider the websites that are already ranking highly for the keywords that you'd like to rank for. Such websites always have a lot of backlinks that you can emulate.
2: Identify What's Already Working For You
You might already have some quality backlinks. Where did you get the backlink from? Did you do anything to earn it? You can probably get more great links by taking things further.
It's also a good idea to reach out to sites that are linking to you. By establishing a relationship, you can become a part of the community and increase the chances for more backlinks in the future.
3: Create Linkworthy Content/Resources
You can create something interesting/remarkable that people want to link to. This could be something like a blog post, infographic, tool. If you invest a lot of time in creating it, then you'll also want to take the next step...
4: Go Outbound
You can go outbound and do link building by contacting people with high quality websites directly and inducing them to link to you (link building itself is a big topic, and there are definitely right and wrong ways to do it). You can try to guest post, or establish real quality relationships with people.
5: Hire an SEO agency to do this for you.
Of course, be careful with who you hire. A bad SEO agency can not only waste your time and money, but hurt your site. Use Monitor Backlinks to monitor them so that you know they are getting high quality links for you.
By taking these actions, it should push up the power of your domain, which should lift all of your pages. As you take steps to get high-quality backlinks, monitor your progress with Monitor Backlinks so that you know what's working.