To add a Contact Form in Squarespace, you can use this guide.
#1. Edit the page you want to add Contact Form > Add a Form Block
#2. Edit Form Block > Click Edit Form Fields
Click ADD FIELD
Then add fields you want such as Name, Email, Phone, etc …
#3. The information of the sender will be sent to your email, add your email address in Storage > EMAIL NOTIFICATION
#4. The information will be sent to your email like this