1.
you have to insert the credentials in config.ini, so to get the credentials you have to create a database first.

2.
on a Linux-Webserver type: crontab -e in your account.

Insert something like tis example:

*/15 7-20 * * * wget -q http://localhost/selfoss/Update --output-document=- >/dev/null 2>&1

Save.

The above example will update your feeds every 15 Minutes everyday from 7 to 20 ...

Otherwise 'man 5 crontab' will help...