open "c:\your\file\name\filename.ext" for input as #1
Now, to read from the file you just opened, use the following code:
input #1, yourvariable
That reads the first group of letters, numbers, etc before the first comma to the variable 'yourvariable'. To read to two variables, you put a comma in between the two variables like this:
input #1, yourvariable, yourvariable2
The above code reads the characters before the comma to 'yourvariable', and the characters after the comma to 'yourvariable2'. You can do this an unlimited number of times. That's about all there is to it.