Each mission can be assigned objectives through the "Interface" section in the worldbuilder, but to get them to show up in the game, you need to make some changes to the overrides.xml file that is in your map's folder.
Primary/Bonus objectives are handled by a simple flag, and are shown in my code snippet below.
So, what you need to do is align your mission objectives in worldbuilder with the ones inside your XML file, and the result, becomes something like this:
Code:
<?xml version="1.0" encoding="UTF-8"?>
<AssetDeclaration
xmlns="uri:ea.com:eala:asset"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Tags/>
<Includes/>
<MissionObjectiveList
id="ModuleTag_MissionList">
<MissionObjectiveTag
Description="OBJECTIVE:RSA001_1"
Script="OBJECTIVE:SCRIPTRSA001_1">
</MissionObjectiveTag>
<MissionObjectiveTag
Description="OBJECTIVE:RSA001_2"
Script="OBJECTIVE:SCRIPTRSA001_2"
IsBonusObjective="true">
</MissionObjectiveTag>
<MissionObjectiveTag
Description="OBJECTIVE:RSA001_3"
Script="OBJECTIVE:SCRIPTRSA001_3">
</MissionObjectiveTag>
</MissionObjectiveList>
</AssetDeclaration>
To actually have text in those strings, create a map.str file and put it in your map directory.
the Script="OBJECTIVE:SCRIPTRSA001_1" tag is when you roll the mouse over the objective arrow, and it is displayed when the camera initially shows the objective.
the Description="OBJECTIVE:RSA001_1" tag is shown in the objectives hud (O key)
BuildMap.bat your map from there.
Hope this helps anyone who has been looking for this.