This article explains how to share Google Drive folders and collaborate on files. These instructions are for the web version of Drive; it works similarly in the mobile app.
Google Drive: Sharing and Collaboration
Google Drive is great for collaborating with colleagues on a project. It offers fine-grained control over who can see your files and what they can do with them. Collaborators can be set to only view or comment on your documents, or they can be given full editing access. Here’s how:
Open Google Drive and find the file you want to share.
Right-click the file and select Share > Share, or open the file and click the large Share button in the top right corner of the page.