There are two ways you can enable the Command Line Interface. Please follow the steps given below:
1) Go to Tools menu > Worksape > Customize
2) Switch to Options tab
3) Select LTE workspace from the dropdown list given under Workspace. (Please see image below)
You can also enable Command line by Command Line Palette icon.If the icon is not available on any toolbar, then you can simply drag it out of the commands tab in Customize window and drop near any toolbar. (See below).