Need to setup custom doamin

[shell kode]

We just started using Jira(with 10 users free plan)
we want to use a custom domain for our Jira page. 

We checked some docs, but under the general settings, we are not able to find the Base URL option to set the custom domain.

[Nic Brough -Adaptavist-]

Changing the domain of an Atlassian system is not just changing the base url, you need to do all the stuff about acquiring a domain and setting up all the DNS to get to it.

On Cloud though, domains are not customisable beyond changing the <your name> in <your name>.atlassian.net and that has to be done by Atlassian.  You will need to raise a support request to get that done, they will not do it frequently, and they will not do it for free or starter accounts.