To import your WordPress blog into Squarespace, you can use the built-in Importer tool. This tool will allow you to transfer your WordPress content, including posts, pages, and media, to your Squarespace site.
For smaller WordPress blogs, follow these steps:
Go to the Advanced Panel > Import / Export > Import.
Click “WordPress”, then click “Basic”.
Enter your WordPress URL, Login and Password.
Begin Import
There is also a guide for larger WordPress websites here.