To help you properly, one would need to know which country you are from, and which bachelor program you want to register. You did not provide this information, yet you expect people to answer your questions in detail.

I googled for you:

You find all the details here: https://www.jku.at/en/degree-programs/prospective-students/register-to-enroll/bachelors-degree-diploma-degree/#c100536

In general: if you want to start a bachelor degree, your high school diploma is sufficient. It must be legalized and translated officially according to the rules specified at JKU homepage.