The example code is here:
http://www.usbuirt.com/api_example_code.zip
It's about 128K and contains 3 zip files:
trydrvvb1_1_0.zip - VB6 sample
trydrv_0_52a.zip - VC++ 6 sample
UsbUirt_rev1.zip - .NET (C#) sample with wrapper and test app. Wrapper can be used with VB.
To get the .NET stuff working, make sure you set the target platform to x86 as the dll that it makes use of is 32-bit.