hi Bichur !!
you choose 1 png as the first frame
this is the starting point
you have to duplicate the I frame + make some change (rotate\zoom)
you got the II frame > duplicate the II frame make the change > you got the III frame and so on
to assemble the frames together : copy the II frame> open the I frame> using the "special paste" feature paste on the right side and go on
the strip will be horizontal !