How to install NXT / EV3 software on Windows 8.1 RT
Sadly that's a limitation of Windows RT - there's no way you can install the EV3 software on there.

Windows RT can only run apps from the Windows Store (and some specially compiled apps that MS supply such as Office RT - however I don't think the typical user can install a correctly compiled non-Store app on the Surface - as a developer you can side load your apps for testing, but they are still Store apps).

Technical Aside:

Windows RT is compiled to run on ARM chips, which are similar to the ones in a Phone or other tablet device - as such applications such as EV3 which are compiled to run on "x86/x64" chips will not work - it's similar to the difference between x86 and amd64 - these were different chips, with different instruction sets.

LEGO would need to produce a Windows Store version of the EV3 software, alongside any other mobile versions and - sadly for you and me (yes I've got one too) - there probably isn't enough market penetration to justify it yet...