Q: Accessing videos shot on iPhone on iMac

They don't magically go anywhere. You will have to plug the phone into your Mac and import them to "Photos", or using Image Capture. Once you've done that, you can do what you want with them.

Hi so basically go to settings

then sign in for Apple ID and icloud

after go to 'photos' app and click photo stream or if you are after a video click on video

Excuse me? What are you taking about? Videos do NOT upload to PhotoStream.

You can put them into an Album and share them via iCloud Photo Sharing, or you can Import them to your Mac and then sync them back to your other devcies. Videos are not a part of Photo Stream:

iCloud Photo Sharing FAQ - Apple Support

iCloud: iCloud Photo Sharing overview

PHOTO IMPORT IOS TO MAC/PC

iTunes 12 for Mac: Sync iPod, iPhone, or iPad

Cheers,

GB

Do you mean upload to iCloud photo library

You can start using iCloud Photo Library, but personally, I am not a fan. Videos will work with this, but they don't work with Photo Stream.

http://www.apple.com/icloud/photos/

iCloud Photo Library FAQ - Apple Support

I am more of fan of importing the videos using the cable and connect the phone to the Mac.

Import photos and videos from your iPhone, iPad, or iPod touch - Apple Support

iCloud photo library gives you access to all of your photos and videos on all devices and keeps them in sync, but you have to pay for the storage and if you make the mistake of deleteing something on one device, you will delete it everywhere.

No - that is not how it works....As both KiltedTim and I have stated, Videos are not a part of Photo Stream.

GB

I would suggest that if you are traveling and do not have access to the Mac, that you use iCloud Photo Sharing. It is easy to use and does not involve changing your current configuration in any way.

Cheers,

GB

Photo Sharing allows you to share with your iCloud email address, so any device that is signed on to that address will get the shared album.

You can use iCloud Photo Sharing from Aperture (go to Aperture>Preferences>iCloud):

Cheers,

GB

Not necessary - it works the same way whether you have it set up on Photos, iPhoto, or Aperture. You can only have it set up on one, but it does work from any of them.

Cheers,

GB