I actually think this question was better on the topic.
To sum up, you can "place it right there on the function declaration importation", but the VB6 IDE doesn't know how to debug such a thing. But the compiler deals with it just fine. Once you compile it into a dll then your main project can access the functionality that was compiled.
Perhaps you are asking how to move these into a dll? If that is the case, you need to create a new Project of type "ActiveX Dll". Name it something like PwrUSB. Next, add a class (or rename the default/empty one if it is provided) to something like PwrUSBApi. Next, in the properties window, set the class to GlobalMultiUse. In a module called MDeclares, drop in all of your declarations:
'from your other post...
Public Declare Function InitPowerDevice CDecl Lib "PwrDeviceDll.dll" (ByRef firmware() As Byte) As Long
Back in your PwrUSBApi class:
'forward your calls to the dll
Public Function InitPowerDevice (ByRef firmware() As Byte) As Long
InitPowerDevice = MDeclares.InitPowerDevice(firmware)
End Function
You could create a more fully fledged object model from the API, but I'd start with this simple wrapper until you sort out all of the APIs.
Oh yeah, back in your main project you'd add a reference your new wrapper PwrUSB.dll in the Project menu. Then in the code you would use it something like this:
Dim numOfDevices as Long
Dim firmware() As Byte
Redim firmware(0 to 31)
numOfDevices = PwrUSB.InitPowerDevice(firmware)
Good luck.