you need to use the open command.
Here are a couple examples:
open file, read 1st line into variable "data"
Open (App.Path & "\filename.txt") For Input As #1
Line Input #1, Data
Close #1
msgbox data
Open file, run through the file doing something to each line:
Open (App.Path & "\filename.txt") For Input As #2
Do Until EOF(2)
Line Input #2, grpfor
msgbox grpfor
Loop
Close #2