The subdomains are not available in the Free Plan. You need to be on a paid plan to update the subdomain field and to brand your sharable links when sending them to your buyers.
Allowing your subdomain to show your sharable links as
((yourcompany)).alongspace.com
Create your 1st subdomain
Creating a subdomain can be done by going to the "Overview" section in your team settings. Here you can add the subdomain that you would like to use for your company.
Update your subdomain
Be careful when you change the subdomain in your team ⚠️
When you update your subdomain, you ultimately invalidate the previously created subdomain links that you shared with your buyers. All old subdomain links are no longer accessible for your buyers. Only the newly created subdomain links will grant buyers access to the spaces.