External code generating for measuring point

What is external code?
What is code for measuring point of external site?

Process:

1. Click on "Banners" in a plan
2. Copy URL for click measuring from field "3rdPartyRedirect:" Insert it to text file (as you need it in point 6).
   If you have more measuring points in a plan, you should save the URL separately for each of them 
3. Go back to list of plans in a campaign
4. Click on "extrnal" in a plan
5. A page with measuring point opens
6. Insert URL for click measuring (point 2) into a text field marked as e.g. URL for click measuring.
   Save the code into a text file or send it on e-mail:
   • Choose person/people who you want to send the file with code to in part "Send code to" or
   • Insert e-mail adress of recipient (s) in the field "and to" d
7. Click on "Send""
8. The code needs to be inserted into site, were a banner should be displayed.

How to insert measuring point into web pages?