Hi

Select cell/cell range;
Select Format Cells from menu or from drop-down opened by right-click;
On Protection tab of Format Cells window set protection options:
   Locked - cell contents will be protected when selected.
   Hidden - user will see only results instead of formulas. Nothing is
displayed  in formula bar when the cell is selected, or in edit mode.

Protection setings will work only when the sheet is protected. When the
sheet is unprotected, the user can edit any entries without any
restrictions.
My advice is to select at start the whole sheet, and set main protection
options. After that, select ranges where you want different protection
options, and reset them.