When you first set up a space, Scroll Versions is not enabled. To use it you will need to enable it.
The space is likely to look similar to the screen shot below:
Either Click on Space tools and select Scroll Content Management or click on the Scroll Content Management hyperlink.
Now click on Set up in this Space.
To enable Scroll Versions, click Enable Version Management and Permalink Support. Then scroll down.
Select the appropriate group that you want to be the Doc-Admins for this space. In the example below, I have selected Confluence-Users. Then click on Save.
You will then see a page similar to the one below. You can return to the space by clicking on the hyperlink for the space in the top left corner, as indicated below.
You will then see a page similar to the one below. The Top-level page for this space has been highlighted.
NOTE: 
If you don't see the Top-level page, then you need to follow the instructions here Show Top-Level Pages In The Page Tree
