On 6 June, the event will already be well underway as the Sun rises in Ireland, and the transit will end not long after sunrise. Earliest sunrise in June in Ireland occurs in the far NE of the island, so the Antrim coast gives the longest visible duration here.
Venus will appear as a small black dot, just at the limit of naked-eye visibility, slowly moving across the face of the Sun, so a telescope or binoculars will be needed to give a proper view. But NEVER look at the Sun through a telescope or binoculars without proper filters - see safety warning below!
The IAA will run a public viewing session at the Car Park at the East of Garron Point, on the A2 Coast Road, between Carnlough and Glenarriff, starting at 04.40 a.m. The transit will first become visible from there when Venus rises at 04.47. The end of the transit will start at 05.37, when the small round disc of the planet starts to pass off the edge of the Sun, and that process will be complete at 05.53, when the disc of Venus has completely passed off the face of the Sun.
SAFETY: It is very dangerous to look at the Sun with any sort of optical equipment, particularly telescopes or binoculars. Direct observing should only be attempted with proper safe solar filters. If in doubt about your filter, don't look through it.