How to Enable and Use Co-Authoring in Excel for Real-Time Collaboration

Step 1: First of all, you need to share the Excel sheet to collaborate with your team.
You can find the Share option in the top right corner of the worksheet.

Step 2: Clicking on it will take you to the sharing window. Here, you can invite collaborators directly using their emails or names.
Just type the recipient’s e-mail and press Enter. You can add as many collaborators as you want.

If you don’t wish to share the workbook through email, you can send a shareable link instead.
Get this link by clicking the ‘Copy Link’ option right below the email bar.

Step 3: Allow Edit Access You can modify the collaborators’ access level by clicking on the Edit option (pen-shaped icon)
right next to the email bar. Set it to ‘Can Edit’ to allow co-authoring in Excel. 

Step 4: Collaborate on the Go When your team members accept the invite and open the workbook,
they can start editing right away along with you. You can see their names or their initials on the top-right corner of the worksheet
if they are actively using the workbook.

The co-authors’ initials will appear in the top-right corner along with their highlighted active cell.

Moreover, in a shared workbook, you can see what other people are currently working on.
Their current cell position will be highlighted with a unique color.

Credit : https://www.simonsezit.com/article/co-authoring-excel/