In order to ensure appropriate transaction security for both buyers and sellers, Poshmark doesn't allow promotional links to off-platform commercial websites.
For enterprise sellers, we recommend including a non-commercial website, such as a social media profile link, in that field, as a means of driving seller credibility and brand-building amongst shoppers.
To add / change the website on your profile, visit here: https://poshmark.com/user/edit-profile.