There are a few things to consider when creating an Instagram or Twitter page for a startup app. First, decide what kind of content you want to share. This could be anything from behind-the-scenes looks at the app development process to tips and tricks for using the app. Once you have a content strategy in mind, start creating and sharing great content that will appeal to your target audience.
Make sure to use relevant hashtags and to tag other relevant accounts in your posts, in order to reach a wider audience. Finally, don't forget to promote your page on your other marketing channels, such as your website and email newsletter.