Westside — I want to exchange the product as it is bigger

Address:

9633653325

Https://www.westside.com/products/ascot-mauve-relaxed-fit-polo-t-shirt[protected...⇄

I bought the above-mentioned t - shirt XL, But it is bigger, so want to exchange with large, I can't see any option to return and exchange. its delivered Aug 18th and try to exchange
Please help for exchange