Hello New to forum and do not know how to fill in my log book can anyone enlighten me please
There's several ways. In order of easiness they're probably:
Find the hill using the hill finder and click on the "log the hill" link.
If you used a GPS when you visited the hill then load the GPX track into the GPX mapping app and a popup will offer you the opportunity to add those tops it thinks you visited to your log.
Write a walk report in the forum - once you've identified your start location and how far you walked you'll be offered a list of tops you may have visited.
Go into your log book in your rucksack (link top right) and edit the list from in there.