Note: Easiest setup would be to connect your Etsy Store to Rollo Ship Manager.
To update your Etsy settings so it generated 4x6 shipping labels:
1) Sign in to Etsy.com.
2) Click Shop Manager.
3) Click Orders & Shipping.
4) Click View shipping labels.
5) Click Options.
6) Select Format my labels for 4x6 Label printers.
Please note that after you change the label format to 4 x 6, only new labels will be generated correctly. Kindly void any previously generated labels and create new ones.
Article content source: https://help.etsy.com/hc/en-us/articles/360001968348?segment=selling