FIeld configuration schemes are not available if you are actually using a next gen project in Jira cloud. In case you are using a classic project you can assign the field configuration scheme to a project like it is outlined in the article which link Carlos posted above.
Probably you are looking for Screens (organised in Screen Schemes) instead?
The documentation is to be found here:
Jira is a powerful tool that helps teams to plan, manage, and report on their work. We love using Jira, especially for its ability to track issue progress. But how to monitor the...
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