The system macros (defined in \sys_resources\vm\sys_assembly.vm) already include the #startAA<object> and #endAA<Object> macros. You only need to include them in your custom macros (stored in the file you cite) or in manual Velocity in your Template if you want to allow editing of the fields using the Active Assembly interface.
When I try adding calls to #startAAField and #endAAField to a macro I’ve written to display multiple-valued fields, it doesn’t work. At the bottom of the Active Assembly interface the following message is displayed:
FATAL exception raised: 'this.objId.getFieldLabel()' is null or not an object
Is this a bug I should raise with support, or does Active Assembly just not work with multiple value controls like sys_DropDownMultiple?