You can easily restore a database backup using phpMyAdmin.
First, you need a backup copy (usually in the form of a .sql or .gz file).
Then, you can log in directly to the database via phpMyAdmin by clicking [Webhosting] → [Databases] in your control panel and then clicking the "database icon" to the right of your database.
After logging in, please make sure that the database is selected in the left column. On the right, you should then be able to see all the tables contained in the database.
Please scroll all the way down and select the option "Delete tables" (or "Drop Tables").
Now click on "Import" at the top and under "Choose file" select the backup file. When you click "OK" at the bottom, the import process will start.