When you/re stuck in the program press Reset and check the settings under Options. Certain checkboxes block certain actions (manual, p.20). Check uncheck Split will also help.
Do Case Mars. (as the manual on p.1 in About says). The instructions are step by step outlined in the manual (p.29) and in the video. It covers almost all of the features of the program. The necessary maps are in Examples subfolder: case Mars.elv and case Marssrf.png, therefore col15bg0.elv is no longer needed. Use VLC player to slow down the speed and for chapter selection (tab Playback).
Ref alt(itude) is a quick way to enter emin-emax, so for scaling and stretching only.
As for the 64x64 map, I forgot to mention that a 64x64 map at level10 covers half the planet, 20,000x20,000 km for Earth, a level17 tile covers an area of 2x2 km with a resolution of 8 m per height point.
Wikipedia says Wallis island area is 96 km2, so a 5x5 map covers 100 km2, location -13.29 S, -176.20 W. (Google). Enter this location in Tile Calculator (uncheck band first), press Calculate, you see a crosshair in the Surf box. Press + several times under Surfbox, at level8 it starts to appear. Press + to level14. This tile covers almost the complete island. Set crosshair at left top in surf box and press + to level17. Tile has band 4696 tileno 168. So a 8x8 map at this location: l17b4696t168. To be safe make a 10x10 elv map at l17t4695t167.
When the elv map is ready, set archive selector to archive+cache, orbiter folder to orbiter root and planet to Earth, press Reset. Enter the location in Tile Calculator l17, b4695, t167 for 10x10 elv map. Then check Split and Write and press Start. Press Calculate a this location, you will say the new tiles.
As for the greyed out buttons, there is logic behind this. When splitting, stitching etc. focus is on centre field, you do not want to loose it when navigating in the surfbox, only to see a suitable location is allowed. When you split you will not magnify. Stitch to lower tile and Merge needs a background, the foreground may not be in the archive or cache. Repair borders excludes splitting, because you use the same Write and Start buttons. You can scale and split at the same time, scale a left tile and turn it to dtype=8 (only when emax-emin < 255). Import and Export is for centre field only. And so on. Read the tooltips. Read PlanetTextures.pdf.