Congrats on your inheritance, agree with GilsTR definitely worth getting yourself & TR in contact with owners/club a support system you'll find TR6 owners you can meet with to give you live demo on how to. Forcing or incorrect way can result in creating hole in top or damage to plastic windows. Having how to video is one thing how to post it is an issue. Bentley's The Complete Offical Triumph TR6 & TR250 1967-1976 Lowering the Soft Top has instructions with pictures.
From Bentley:
Push the header rail, rearwards and slightly upwards, while knocking the soft top side support downwards until the assembly begins to fold. Continue lowering the frame and pull the fabric flat over the deck lid. Fold the fabric forwards over the soft top frame and turn the ends of the fabric inwards. Ensure, that the Vybak windows are free from distortion and that the fabric is clear of the frame
TR6 Owner:
Detached top from velcro on frame over each window, unsnap fasteners attached to bow/frame inside, middle & rear of top and 3 snaps outside both sides. Unlatch catch levers (except at the front rail the soft top separates completely from the frame)
Grab front rail with one hand lift up & pull towards rear of TR at half way point grab soft top at rear with other hand and pull top off frame, with frame folded & behind seats soft top should be pulled towards rear laying flat across trunk. (Should look like pancake version of top up)
Bottom of front rail now visible, top smoothly stretched over trunk, plastic window against side of TR. Fold soft top towards front (back of seats) then fold windows in. Care not to force anything as it will all fall into place. Again a thousand words vs hooking up with someone who can demo it to you changes frustration into success!
Since you're a TR6 NooB putting soft top up especially in cold weather can be challenging at best due largely to cold fabric. Unfold soft top, grab front rail pull up & foward, latch to windshield frame, stretch/attach top sides to velcro. Consider yourself fortunate to be able to snap 1st 2 snaps on either outside (last snap near rear window you may have to drive in the sunshine for fabric to warm a bit) then snap flaps over inside bow/frame. Once tops been warmed by sun unsnap 3 snaps and resnap rear to front both sides