The problem you have is "VT-x is not available"
There can be several reasons for that, but basically this is not related to ThingWorx Analytics, you would not be able to start any other VM in virtualBox either.
This usually means that virtualization is not enabled on the Bios, so you could restart you machine and check the BIOS if this is set.
However, VT-x could be enable but still get issue if there are conflict with other hyper visor. For example you may have to disable Hyper-V in Windows (Control Panel > Program & Feature > Turn Windows Features on or off )
Also if you are running your machine on the cloud, you would get this error. You cannot installed ThingWorx Analytics 7.4 directly on the cloud see https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS248425
Hope this helps