One of our MVP's (that knows a lot more about VSTS than i do) indicated finding Shelve/Unshelve can often be difficult to find and uses the command line to access this functionalityas a result .
Having looked for it in the past i am not going to disagree and thought a couple of screen shots might be useful.
After the project is under TFS Source control you should be able to access the Shelve/Unshelve functionality one of the two ways.
1. Bring up the Pending Changes Dialog one of two ways:
View > Other Windows > Pending Changes Right Click a project in Solution Explorer > View Pending Changes
View > Other Windows > Pending Changes
Right Click a project in Solution Explorer > View Pending Changes
In this dialog both Shelve and Unshelve are on the toolbar (see image below)
2. Right click on a project or file in the solution explorer and choose Shelve/Unshelve.(see image) NOTE: The context menu is highly dynamic based on what you right click and may not show Shelve - For instance right clicking on a directory doesn't offer Shelve as an option....