Unlock cells/sheet in a spreadsheet
To unlock a cell range/sheet:
Go to
icon in the top-right corner of the editor screen. Under the Data menu, choose Lock Cells.
Tap on the Manage Lock Settings option.
Choose the desired cell range/sheet to unlock from the displayed list.
Choose the users for whom you wish to unlock the range and tap Apply.

Note: Only file owners and user with share permission can lock and unlock cells.