You can directly edit the contents in the Excel cells, however, you can disable this function. If you disabled editing in cells, you cannot change the content except to delete or re-write them. To enable editing again, please following steps below:
Step 1: Click the "File" Tab from the ribbon;
Step 2: Click "Options" from the left navigation menu;
Step 3: Click "Advanced" from the left navigation menu in the dialog box;
Step 4: Check "Allow editing directly in cells" under the section of "Editing options";
Step 5: Click "OK" at the bottom.