Android Studio expects to see the settings.gradle file in the root directory of its project and likes to have Gradle shell files in the root. If you are trying to open, say, Project1 as an independent project, the problem you are facing is none of these things are in the Project1 directory. If Project1 is just a module in a larger Apps project, this is not necessary.
What are you trying to do? Perhaps there is a better approach, rather than opening a subproject independently.
EDIT:
This works for me if I copy the Gradle shell files ( gradlew , gradlew.bat and the gradle directory) to the subproject directory, and also add the settings.gradle file, which looks like this:
include ':'
Here is a screenshot of my project layout where I edited LibA to be able to open independently:
Please note that if your subprojects are dependent on each other (for example, Project1 depends on Project2), then this scheme will not work. Now Android Studio understands only in the context of a larger project with a root directory that can cover all the dependencies.