It appears that you have downloaded the commercial version of Tekla Structures 2016 from the Tekla Downloads (https://dowloads.tekla.com) instead of the free Tekla Structures Learning edition from the Tekla Campus (https://campus.tekla.com).
You cannot use the version you have downloaded and installed unless you are a paying Trimble customer.
It appears that you have downloaded the commercial version of Tekla Structures 2016 from the Tekla Downloads (https://dowloads.tekla.com) instead of the free Tekla Structures Learning edition from the Tekla Campus (https://campus.tekla.com).
You cannot use the version you have downloaded and installed unless you are a paying Trimble customer.
Instead, you should download and install the software from the page https://campus.tekla.com/download.