If you have been using Office 365 prior to February 2013, you would have been on what is known as Wave 14 or the 2010 versions of the software. This means that your SharePoint site collections (i.e. top level sites) probably looks something like this now when you visit:
You’ll see that it still has the older SharePoint 2010 interface but now there is big crimson banner across the top of the page like so:
What this is letting you know is that it you have the option to upgrade the interface (i.e the look and feel) to the latest SharePoint 2013 version.
For most people who have used SharePoint this upgrade is something that you can do immediately. Where it becomes more complicated if you have gone in a done some major customizations to the look and feel (i.e. HTML and CSS changes) or inserted custom code (i.e. solutions and web parts). In that case, you are really need going to need to spend some time testing these with the new 2013 interface. Also remember that upgrading a site collection will also upgrade all subsites automatically as well.
However, in this case, I know I have a very basic SharePoint site collection so I am going to proceed with the upgrade by selecting the Go to the upgrade page now link in the banner.
That will take me to a page like you see above. Here I have the option to Try a demo upgrade if I want but I am happy to proceed with the complete upgrade so I select the Upgrade this Site Collection button.
Importantly, taking this option means that when the process is complete I will be unable to roll back to the 2010 version of my site, so make sure you are 100% certain that is what you want to do.
You’ll receive a confirmation that you want to proceed with this as it is a one way trip! I’m sure I won’t have any issues so I press the I’m ready button to proceed.
Now the upgrade will be scheduled. It may take a while for the upgrade process to commence so be patient. If you get cold feet you can press the Don’t Upgrade Now button, however if just wait this page will refresh every 60 seconds or so to let know the status. Pressing the Refresh Now button doesn’t make the upgrade process commence any quicker (much like traffic lights).
Shortly, the upgrade process will commence as you can see above. Again, the screen will refresh every 60 seconds or so and provided updated information on the progress of the upgrade.
The time to complete the upgrade process will depend on the size of your SharePoint site collection and the amount of information and sub sites it contains.
Once the process is complete you will hopefully see a Completed Successfully message as shown above. If you want to, you can select the log file link to view technical details about your upgrade. That will look something like:
Which is probably only going to be of use if the upgrade failed for some reason.
In most cases you’ll select the Let’s see this new site button in the lower right hand corner.
Doing so should reveal the upgrade site with an updated SharePoint 2013 interface like shown above.
If you do need to revisit the upgrade log you can do so.
Select cog in the top right hand corner and from the menu that appears select Site Settings.
In the bottom right of the Site Settings screen under the Site Collection features select Site Collection Upgrade.
Now select the Preview Site Collection Upgrade Status link in the middle of the page.
You’ll again see the link to the upgrade log file.
Now what happens if you do nothing and don’t upgrade your site collections to the 2013 interface? It is my understanding (and I am not 100% sure about this) that come April 2014 Microsoft will automatically upgrade any old Wave 14 site collections to Wave 15, but as I said I haven’t found anything definitive on whether this will be case and how it will be conducted. Best advice? Upgrade as soon as you can so you have the control.