What version of labVIEW you are using?.
In labVIEW 7.0, you can use FP IO Point constant to browse the channel from your iak file.
In earlier labVIEW version, you need to use FP open VI and connect the reference to FP create tag VI to create a valid tag reference. FP create tag VI requires device, item and tag names as input and returns a refnum for the particular tag. You can then use ths refnum wired to read or write VIs.All the VIs mentioned are available in FieldPoint sub pallate in functions pallate.
Look at the FieldPoint examples that ship with LabVIEW.