I’m a beginner, and I want to ask, how do I activate hcaptcha when I want to visit our website …?
Are you wanting all visitors to solve the captchs before they get to your site? If so, step 6 in this tutorial covers that, you can create a firewall rule with the ‘Challenge’ action.
does the free plan provide a firewall
The free plan provides 5 firewall rules that you can configure, just not the managed rules.
whether free packages can use hcaptcha ?
Yes, all plans have the action ‘Challenge (Captcha)’ option on firewall rules,
how to set it up, I have 3 domains using CloudFlare, but with a free plan.
You create a firewall rule like the one in step 6 of the tutorial I linked to.