hello,
first, instead of writing main(), you must write int main()
or if you need command-line, you must write int main(int argc, char** argv)
then, you need a project file, create one from file->new->project
and then add your files there, then compile your project

main is a function and eatch function must have a return type
then, you need to create a project and add your C sources there using project->add files or if you want to add everything in a folder, project->add files recursively