If you have access to the database via your hosting phpMyAdmin, you can edit the wp_users table in the database.
Find the record for the admin user in the wp_users table. Change the name, email to the new values. Enter the password you want to use, then use the MD5 in the dropdown for that field to encrypt it. Once all changes are made, save the entry, then log in with the new credentials.
Alternately, you can just change the email address of the admin account (again via phpMyAdmin), and then use the ‘lost password’ function to enter a new password. After logging in, go into the Users and change the name and other information as needed.