VB has built-in I/O support;  look up the Open, Input, and Close
statements, and the Input() and FreeFile() functions, in the VB online
help.

Here's a simple example to read the complete contents of a file (no more
than 2GB in size) into a String variable:

   Dim strFileName As String
   Dim strFileText As String
   Dim intFileNo As Integer

   strFileName = "C:\Temp\TestReport.txt"

   intFileNo = FreeFile()
   Open strFileName For Input As #intFileNo
   strFileText = Input(LOF(intFileNo), intFileNo)
   Close #intFileNo

Note: you can also use methods from the Microsoft Scripting Library to
do this sort of thing, but for simple I/O, using the native methods is
more efficient and reliable.

The usual BASIC syntax works in VBA in Access

Open "myfile.txt" For Input As #1
Do While Not Eof(1)
   Line Input #1, a$
Loop

will work.