How to Collect a post
If you wish to add your own older posts to a Collection without resharing them as new posts and spamming your stream, here is what you can do:
There are two arrows at the bottom of a post.
The bigger one on the left reshares a post.
The smaller one on the right can reshare a post too but also moves a new (uncollected) post to a Collection you have created.
A post that has already been added to a Collection must be removed first if you don't wish to reshare it to another Collection and create a duplicate.
To remove a post from a Collection click on the top right menu dropdown and then click on "Remove post from Collection".
After this you can "collect" the post again from the top menu or from the small arrow at the bottom.
Of course, if you add someone else's post to a Collection, then you will get a new post appear on your profile and your followers stream. You could uncheck the "People that have you in circles automatically follow this collection." from the Collection setting while you add more posts, that may help as the posts are visible only on your profile and for those who have clicked to Follow the Collection.
More about the Collections from Google+ Help Center:https://support.google.com/plus/answer/6210271
See the screenshots for more: #Collections #GooglePlus #Jaanatip