Procedure

1. Identify the token for the system text you want to replace using English Debug. From the name menu, go to Settings > Change Language > English Debug > Switch.

2. Go to the page where you would like to change the label. In this example, we will change the label for the home page from the main navigation menu. Get the value between the colons. In this example it will be: COMMON_HOME_TAB
3. Go back to the name menu > Settings > Change Language and select again your default language and choose Switch.
4. From the Action Search go to Manage Languages.

5. If a custom locale does not exist, you will need to create one. Under the Action column, choose Add custom locale corresponding to the language pack.

6. It is required to enter a new name for the custom language pack such as English US Custom, and choose OK. The custom language pack gets appended to the original language pack.

7. A "+" button in now available in front the language for wich you created a custom locale. Select it.

8. Download the custom.

9. Save the file on your computer. In the first row, the word Key will already be in the column A. Add the locale code in the column B. In this example, it is en_US. Then in the second row, add your key COMMON_HOME_TAB and the label you would like to see, for example Renamed Home Page.

10. Save the file as a V2. It is important to keep the .csv format. Then, import it and upload it in the system using theUpload custom label option. Select the file you created.

11. A message will indicate that the file was uploaded successfully. Choose OK.

12. In order to test the changes, make sure that you use the language for which you made the change. You need to log out and go back to the instance and it some cases it can be helpful to close your browser completely or even delete the cache.
CautionIMPORTANT NOTE
Be careful!
When keys already exist in this file and you want to make more changes to other system text, always download the latest file for the custom label from the system and add the new key to the list but keep those that are already there when you upload. If you just put the one that you want to change in this file and remove the other keys, you will delete the customization put in place for the other keys.
When keys already exist, the cell 1B will have the language code an underscore and the company ID of the instance in which you make the change. To be able to upload this file back into the system, you will only need to keep the language code in this cell and therefore remove the last underscore and the company ID.