When do you want to read from the text file and write them to tags? When somebody presses a button? On a timer? Do you have an example of the text file so we can post an example? You have to use scripting in order to perform that task. The main idea is that you read the text file in, parse it, and write it to tags.
Here is a small example:contents = system.file.readFileAsString("C:\\Path\\To\\File.txt)
values = contents.split(";")
system.tag.writeToTag("Path/To/Tag1", values[0])
system.tag.writeToTag("Path/To/Tag2", values[1])
...Of course yours will vary depending on the text file. The above example assumes the values in the text file are separated by a semi-colon.