The USB input on your TV is solely for accessing external media (such as photos, videos and music) via the TV. See page 77, et seq, in the manual:
http://downloadcenter.samsung.com/content/UM/201701/20170117201300674/MNLDVBEU6E-ENG-WEB-170117.1.pdf
As has been said, you can make your set 'smart' by adding on an external device. For example, a Now TV box will give you access to catchup services on your telly (such as BBC iPlayer, 4oD, etc). It will also let you watch Youtube videos on your set and provide access to other apps. (The full list is here:
http://web.static.nowtv.com/images/NOWTV_2017/13_Docs/list-of-apps-on-the-now-tv-box-uk-dec-17.pdf ). If you choose to buy an Entertainment Pass (£7.99 per month, with no contract) you can get a good selection of extra channels too, such as Sky 1, Sky Arts, Sky Atlantic, Sky Living, Comedy Central, Gold, etc. (There are also 'passes' available for movies and sport).
Argos are currently offering the Now TV box, complete with an Entertainment Pass for 4 months, for just £19.99
http://www.argos.co.uk/product/7471931