To center your panel, subtract the measurements from the target finished size & divide by 2. So your current panel width is 26 and your target width is 54. The difference is 28". You want an even number on both sides, so divide 28/2, which gives you 14" on each side.
your target length is 80 and you have 44 in your panel. The difference is 36. To have the same at the top & bottom, divide this by 2, so you need 18" to fill. Now you have to find a block that will work in both a 14" and 18" space. Personally, I would go with a 6" block. 2 will fill the 14" space and 3 will fill the 18". Then add a 2" border on the 2 sides to make up the difference between 12" and 14". I probably would also add the same border to the top and bottom, making the finished quilt 54X84.
I have worked a lot with vector based (Illustrator) and paint-type graphic programs. I have found the EQ-7 interface to be very different from either one of these. I usually do the actual block design in Illustrator, then use EQ7 for layout for both color and block placement.