A Pitha is the pedestal and space or (vibration) environment of a Devata which is really a/the whole universe. A sadhak by resonance makes the pitha their universe which is seen both within via microcosm and as their own environment.
When viewing a Yantra, one sees various structure depending upon what is represented. Inherent in the yantra is the pitha wherein the energetic manifestations are contained in the coverings. A sadhak, establishing ones own form (in a greater sense) as yantra (instrument), can then manifest the pitha. The center or heart of the pitha is the ishta devata, the mula mantra is the point of resonance with the essence of the pitha. In many ways, if one penetrates and resonates with the essence or center of the pitha, then all other energetic elements are naturally present. If the center of the pitha is the heart, then in recognizing those surrounding energetic elements, one is seeing the various limbs. If one regards a (material) yantra, the one can see that from the center there are usually certain angles (triangles), petals, angles of the hexagon, surrounding space, gates, and more. In these places are different elements of the pitha such as the particular shaktis, forms of bhairava, and more. The tantric sadhak may manifest this environment in their own being and life.
There are different ways to understand and view the pitha as it relates to manifesting it as a sadhak. If one thinks of themselves, then there are often certain elements around. For example, if one enters your company, then they will enter the company of those that surround you (like family, friends, etc.) Just so, when one enters association with a devata, then there are also elements which surround. Of course, this is a very gross example because while in union or Being the Ishta Devata, the surrounding energies are not seen as separate, but rather like ones aura. It is a rather apt example in another way, because often the people that surround a person are a resonant reflection, so in that way also an aura (or projection) of what they are. Moreover, when one truly becomes resonate as the Devata and pitha, then this is not separate from ones “outer” environment. This realization is of two sort, whereby it is an undercurrent and appearances are signs or mudras of it, or it can be pure vision which is literally perceived (not as “visualization”).
Before one has the depth of view to effect the “outer” environment, one internalizes the Devata and pitha in their own being. Further, the naturally contained pithas which are contained within the subtle channels and in bindu come into accord making the inner pitha energized (and satiated=blissful). While the sadhak doesn’t regard the surrounding energy as separate from the essence of the Ishta Devata (or true nature), the mature can still recognize (and play) with the uniqueness of various manifestation without fear of losing the view. Going beyond non-duality means that one is fearless in its understanding, so needs neither reflective reassurance and is liberated to explore the subtlety of uniqueness.
Many people may be familiar with the word pitha as it relates to sacred sites (such as shakti pithas, shiva pithas, etc.). These places offer the opportunity of association, and if open and receptive, then the opportunity of recognition and assimilation. These subtle environments move the pilgrim in subtle ways(even if they are unaware) and plant seeds for future blessing. Likewise, when a person becomes a pitha, then they have effect on those around them (or those that enter that space). To have direct effect is much more true and important than imposing some concepts or words. To embody the pitha is to be a spontaneous walking blessing on the whole environment because the environment cannot help but conform to the pitha. Those of great strength may enter “another’s” environment and even accept/conform to their forms, concepts, and ways, but transform those into mudras of liberation within the pitha. (What this means in demonstration is truly deep, and is skillful action that can only come from that most noble of sentiments.)