Look into traditional, acid free, colour fast, 100% museum board for mounting the photograph to, in position to match the window of a frame able over may.
Lineco, Linen pre-gummed tape, distilled water and a good straight edge.
Draw lightly a straight line a the what will be the top edge of the photograph, centered by the margins on the sides.
Cutoff about of four inch strips and fold equally in half across the width, with the adhesive side facing front and back.
With no distractions or interruptions, use a small sponge brush in a small saucer, with a LITTLE distilled water, and, going from one end of the drawn line, damp wet the side that'll hold to the back board, not the front facing dry taped, laying the hinge of each precisely on the line, in an evenly spaced row, but not overly wet.
Allow the tapes to dry, making sure the hinges are tight to the board and line.
Once the first part of tapping is thoroughly dry, place the photograph in a quick ready position and starting with the middle tape on the board, quickly damp the dry side of the tape and position the photograph in place on the line, applying enough force to get a good adhesion, in line with photograph and drawn reference line.
It might be a good idea to invest a large index card between the two sides of tape, with the second side allowing any runoff of water from making the just taped will have run off to the index card where a sheet of paper towel can pat it up and the already dried side against the board, won't get wet and loose its grip or placement.
Go down the top line, one tape at a time, allowing each to dry to the touch, before going back to the middle side that next needs gluing down.
You should go slow enough that you keep the two top lines, inline with each other and set the matted photograph somewhere safe, without ANY BENDING of the Board.
You should now have a backed, photograph that you can cut a window for, in a second piece of 100% Rag museum board.
Hinge securely, strongly, the two boards at the top of each as you just did with the photograph, for a proper job.