excel training microsoft - Protecting Worksheets

Cells are protected with a two stage process.

All cells are locked by default

By clicking on format > cells, then navigating to the PROTECTION Tab, you will see a tick box saying locked.
You would need to unlock the cells you do not want to protect.

Protection only works once you switch the functionality on.
To do this, click on TOOLS > PROTECTION > PROTECT SHEET. Same to unprotect