General aviation pilot on IFR flight plan described confused VFR on TOP scenario when he/she tried to shorten the flight applying VFR rules; but ATC noted the IFR status and handled the flight accordingly.

Narrative

Upon departure from my home base on an IFR flight to ASW; after reaching altitude of 9000; at which time I was able to contact ZAB; I activated my flight plan. However; I thought I had indicated that my desire was to get over the high terrain first under VFR flight rules; ATC responded with a question of flying VFR on top. This had led to my mistake; as a new IFR pilot; of not connecting the dots of the nuance of VFR on top or flying under VFR rules. The controller very kindly requested to speak to me about what I had done to which I had agreed to in my quest of knowing the right thing about all aspects of flying. The controller had explained; what I had already realized; that is while flying VFR on top and having filed IFR direct to destination; I had no discretion to wander over the mountains in search of the shortest and quickest way to the lower terrain on the other side; but to go over the Taos VOR (TAS) and gain altitude in a hold first before embarking on my direct routing to destination. Or I should have activated my IFR once in the lower terrain and on the other side of the mountains; while getting there under VFR flight rules. In retrospect; the controller was clear; it was solely my misunderstanding or misinterpretation of what I was instructed to do.