Insert waypoint markers starting - obviously - from the start point of your Ai route.
Like so
Press crtl-w or select the edit/waypoint menu to name you waypoint
If you Ai is going to loop contunuously then you need do nothing more in this screen,
But if you Ai is just going to advance from A to B then tick the box waypoint does NOT loop
Now you have defined your waypoint you need to select (highlight them - they turn yellow) all the waypoints and edit their item attributes.
You can at this point change the waypoint radius, the smaller the size the more accurate you can predict the pay an Ai will take.
If every thing has worked they should all now be linked together.
Dont forget thet if you waypoints are for helicopters then you have to change their Z value from the default 0, only if your helicopter is to land do you need the waypoint Z value for the last waypoint to be 0
1 point to remember is that Ai - not vehicles - will leave waypoints if they detect a player unless you set the min engagement distance to 0