You can add an entry or modify the one you select first, by pressing the relevant button in the Bootloader Configuration screen and editing the screen that pops up on top of it. Some things that can be done without any risk, are changing the label of an entry and ticking the box to make an entry the default one. Sarrera bat bertsio-multzo egokia gehi dezakezu, edo erabat berrizendatu. Lehenetsitako sarrera bat du sistemak ez baduzu aukera bat egiten abiarazteko honetan sartu eta abiaraziko da. Editing other things can leave you with an unbootable system. Please don't just try something without knowing what you are doing.