Inside the desired kapp inside the desired space, selecting Forms will take you to the forms console. This console displays all of the existing forms in that kapp (if any) and allows you three ways to create a new form:
Each of these methods has pros and cons.
Creating from scratch means you are starting fresh. There is no need to clean up any potentially unused or problematic fields, elements, bridges, or functions. However, many kapps require forms have certain elements on them to function properly. Starting fresh can mean having to recreate fields, elements, or sections already in place on other items.
Importing is essential when moving elements between environments, such as from development to test and from test to production, but it is unlikely to be an effective or effecient way to develop. While it is possible to develop by typing up all of the appropriate json, it forgoes the friendly form editor provided.
Cloning allows for development using the form editor, but you inherit all elements from the existing item. You may not need all the elements, fields, bridges, etc on the form that was cloned. This leads to potential clean up.
A good in between in using the Create Form to create the initial form for the kapp with all of the required fields, elements, and such. This may also mean creating any forms that will be used as subforms in the main form for the kapp. Once that primary form is built with a main placeholder field, name it as a template and always create forms off of that. Make sure to always start from the template and keep the template up to date if changes are needed.