Hello STORMM,
Yes, you need to install all updates, in order of appearance
So first the update all versions to 1.3.5, then 1.3.5 to 1.4 etc all the way to 1.5.5
http://www.shipsim.com/downloads/updates
You can check the version by clicking on Options, the version will show in the bottom left corner of your screen.
By the way, it seems all official servers are off-air at the moment..