please understand, i'n not fully understanding of you question.if I do this is it. Remove the trim around your problem window and secure your frame to it if this is not plosablecontact someone with the skill to do so, I cannot determine a sollution without seeing the prob. I assume ? yeah, assume, your wall is approx. 15x12 guessing? use that as ref. with a window dead center of this wall. if correct you need to remove existing trim.there are studs behind this trim. incorperate this window to accomodate your shelf purcha. maybe if you cant afford extrs trim work at this time you can always wait a week or two to purcha. this accom. if this ia not a plauseble sollution request a free estimate via this same spot. if your not too far away I can help if not call a carpent, he may be closer thatn you think, and able to help you for a small fee if not request me I can talk you through this if you have any skill towards woodworking at all.being you took on this venture,i'll guess you do so stay in contact, I'll help as possible.Good luck man! Call back with prob. via personal request. just remember expect the worst hope for the best. hopefull to help you anyway poss.
