Sorry, my fault, should have been clearer, don't drag the mouse, use the right button and click along the taxiway center line making sure to click on the hold lines as you pass them,
as you go along you'll end up with red dots like this, you can see the black dots where it passes other taxiway's, make sure there is a black dot or the aircraft cant follow the route. see the second dot from the top, (which is on a hold line at KLAX) is green, left click a dot and it is selected and shown in green
if you left click on a dot where you want to add a hold with the left button, the dot will change green to show its selected, then fill in the edit box as below with the appropriat runway numbers.
Name is the taxiway ID, for example "M"
It needs to be a simple two way taxiway at adount 70 to 80 foot wide.
Hopefully that helps.
Gareth