To lock an entire sheet in Google Sheets, right-click on the sheet tab and pick the Protect sheet option.
How do I lock an entire sheet in Google Sheets
Next, enter a description for the sheet and click Set permissions.
The Protected Sheets and Ranges Menu
Finally, under the Range editing permissions, select Restrict who can edit this range and choose the option Only you. When finished, click Done.
Range editing permissions in Google Sheets
And there you go!