This example tells you how to increase player 1's titans speed by 2. Please note that the field is a number, NOT the actual field. Each field is coded by a number starting with 0. To work out the number, go to the editor and go to the modify protounit box. The fiel dropdown box is in the code number order. To work out the field number, start from the top field on the dropdown list and call it zero. Now count down the dropdown list adding 1 every time. Stop on the fiel you want to use. The number you gave it is the code number for the fiel box. E.g. speed field number is 1 because it is the second item in the drop down menu. If you wanna use modify protounit, copy this template into the effects part of your trigger section of your random map. Just change the stuff you need to which is either the unit, player number, field number or Delta number. I hope this guide is useful! (This is probably the only bit of scripting I understand for this is the only thing I have worked out for myself!)
rmAddTriggerEffect("Modify Protounit");
rmSetTriggerEffectParam("ProtoUnit","titan atlantean");
rmSetTriggerEffectParamInt("PlayerID",1);
rmSetTriggerEffectParam("Field","1");
rmSetTriggerEffectParamInt("Delta",2);