First of all, you can do a prospecting campaign to know which users from your target audience are interested in your brand. They will be the ones who click on your ads, visit your site, etc.
With that data, you'll be able to start your retargeting campaign, reaching those users who interacted with your brand previously. This way, you'll increase your conversions in a more efficient way since you're paying to reach users who you know have an interest in your brand.