The backlink score is a combined score that is based off of two metrics that are provided by our backlink data supplier, called Majestic. These two metrics are called trust flow and citation flow.
They are metrics to determine the total value of the website's backlinks. The higher the number the better and more authoritative a website is. So you want to aim to increase this number over time.
With regards to increasing this figure, this occurs when your website accrues more backlinks, so you need to build more backlinks to your website to improve this.
We are going to add a feature in 2019 that will provide recommendations on building new backlinks, but in the meantime there are two recommendations:
Work through the recommendations in Local SEO for adding your website to authoritative directories
Distribute your existing and new content via methods that may build new links, here's a guide - https://hikeseo.co/how-to-redistribute-content-for-visibility-seo/