This is my first post so please excuse the stupid question...I am not very technical.

When topping up the screenwash this morning I noticed that the coolent levels in the reservoir in the top right hand corner of the bonnet were on 'Low'. I have a coolent alarm which hasn't gone off at all but I'm pretty sure the coolent hasn't been changed since we bought it in 2.5 years ago (28,000 miles).
1. Can I just top it up by opening the reservoir and just chucking in some more coolent or will that knacker the engine with air locks etc?
2. If that is the case then what coolent should I use?
I am worried about this as I live in Holland and the local mechanics have no experience of Bongos.
Many thanks in advance

WIDBongo