Apologize @arunshankar, I have missed this completely.
Download the bulma.css from the following link
https://bulma.io/
In Portal Management:
1. Under Content > Web Files> Create new
2. Name and partial URL as" bulma.min.css". The screenshot below for your reference

3. Hit Save.
4. In the notes tab > upload the bulma.min.css file. Screenshot for your reference

In Portal Studio:
Press sync configuration and browse the website.
Now from Bulma documentation, you can use any components, layout or form components as per your need without writing any custom JS
https://bulma.io/documentation/
Hope it helps.
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