I purchased a SquareSpace domain and created my website with Visual Studio Code on my system. Surprisingly there is no easy way to upload these HTML, and CSS files from my system to SquareSpace. Any help is appreciated.
Solution After following the vital response, here is the solution I used.
A website has two aspects: a domain name, which is provided by Squarespace, and you need a host to put your required codes.
There are many options to host your codes for free, and among them, GitHub is the most popular choice.
Since Squarespace does not accept forward slash in the domain name alias, you need to create a GitHub account with your domain name. Then, you need to create a repository with the following format: .github.io (ref. https://docs.github.com/en/pages/getting-started-with-github-pages/about-github-pages#types-of-github-pages-sites). In this way, your GitHub page, once published, will not have any forward slash.
After this, first, you need to publish your website in GitHub, which you can easily do by following this link: https://www.youtube.com/watch?v=4eMnz8VbgyM&t=18s (this is not in English, but I think it would not be a problem).
Next, you need to change the DNS record in Squarespace, which you can find at https://account.squarespace.com/ -> DNS -> DNS Settings, and this link can guide you: https://www.youtube.com/watch?v=EX4w9hsduNA.
Note: Before adding CNAME for your GitHub domain in Squarespace, you need to delete default DNS settings, and you probably need to wait for some time so that the domain name is available for every DNS record.