Announce your brand presence on Instagram
Of course, your brand also has an audience outside of Instagram, such as your site visitors, your email subscribers, your followers on other social networks such as Twitter, etc.
One of the best ways to increase followers is to announce in all your other media that you are on Instagram and what is the advantage of following your page on Instagram.
For example, have a section on your website for the latest Instagram posts so that users notice your presence and to some extent your content on Instagram.
Remember that you should not only ask them to follow you on Instagram, but you should give them a reason to follow you. And the best reason is to publish useful and different content from your other media, otherwise there is no reason for your Twitter audience or your site visitors to follow you on Instagram.