It's not compulsory to have attended such a course if you want to observe elections, but it probably helps. Just to review how you actually apply to be an election observer, US citizens go here, UK citizens here, Canadians here, Dutch citizens here, Belgians hier and ici. Irish opportunities are listed here, though they don't give the contact for OSCE missions (but I know who it is, so email me if you want to know).
It does help to know which elections you want to observe. The following, all due before the end of this year, are likely to attract international observation missions:
Macedonia Parliamentary, 5 July
Turkmenistan Municipal - Village Councils, 23 July
Bosnia and Herzegovina General, 1 October
Bulgaria Presidential, probably November
Georgia Municipal, November though rumours say they may be postponed
Moldova Election of Governor of Gagauzia, Autumn
Montenegro Parliamentary and Municipal (probably separately), Autumn
Tajikistan Presidential, Autumn
Albania Municipal, Autumn (TBC)
Turkmenistan Municipal - District and City Councils, 3 December
Let me know if you are interested in any of these and I will do what I can in terms of other information.