|As per the instructions given at the link I suggested...|
Open the VBE (Alt+F11) then double click ThisWorkbook to access the private module of the Workbook Object.
(You can also open the VBE by right-clicking a sheet tab and choosing View Code. Then double click ThisWorkbook.)
Paste the code in the ThisWorkbook pane and you're done - sort of.
One thing that is not discussed at the site, is how you, the author of the workbook will edit your formulas since they are hidden and locked.
First, you will need to unprotect the workbook using the password that is given in the code. (You can change this password by replacing "Secret" with whatever you want.)
Then you need to temporarily stop the macro from running whenever you select a cell and edit it. You can do this by putting an apostrophe before the word Private. Once you've made your changes, remove the apostrophe and the code will run - and protect the worksheet - the next time you select any cell.
Finally, if you don't want your users to view - and possibly edit - the code (which contains the password) you'll need to hide and protect the VBA module itself.
Right-click the ThisWorkbook module and choose VBAProject Properties, Protection tab.