You may need to create a full-width page template if your gallery is showing as very thin when you embed it in a page. This takes no knowledge of coding to do.
1. Click Online Store and go to Themes
2. Click Actions beside the theme you're using and select Edit HTML/CSS
3. Under Templates, click Add a new template
4. Select Page from the drop-down menu and name it "fullwidth"
5. Delete all the code in the template and paste this code:
6. Click Save and go to Online Store > Pages
7. Select your Instagram page and from the Template dropdown menu on the left, select the page.fullwidth template
8. Click Save and then View to see your changes