Very new to SharePoint and would like some help with collaboration. Other than AD, I have all Office 365 (email, install Office products from cloud, etc.) I've created very simple sub sites to the default site. Since I'm still testing, security is wide open at this point. I've uploaded a 2010 Excel file that I'd like 3 users to collaborate on. It's a schedule that all three need to keep open, and update during the day. I've search the web and it looks like an easy process. Create document library, make sure check in\out is disabled, and add file. But when User1 opens the file and User2 opens, User2 gets read only. I've searched the web and can't seem to find any straight forward information. Below are a few details.
Office 365 Rev15, Office 2010 installed on users computers via Office 365 site, all plans are E4, URL to the document library is: https://companyABC.sharepoint.com/departments/FS/_layouts/15/start.aspx#/
Again, I'm very new to this, so if I'm missing any important information, please let me know. But any answers, or suggestions to where I could get answers would be greatly appreciated.