Have a width and a height metafield
In Shopify, open Settings → Custom data → Products. The width and the height each need a metafield of the type Dimension, Integer or Decimal.
A Dimension metafield states its own unit: mm, cm, m, in, ft or yd. An Integer or Decimal is read in the unit under Sizes without a unit are in, on the Posters tab.
Connect them in the app
In the app, open Products, then the Data sources tab. Choose your metafields under Width source metafield and Height source metafield, and click Save.
This applies to the whole shop. Your metafields win over the Poster size set in the app. A product with empty metafields uses the Poster size set in the app.
Check the products
Open the Posters tab. A product with both metafields filled shows its size. To check one, click Edit, then Preview.
Need help?
Tell us which product and which step, and we will help. Email support@seeonwall.com.