1. Open TexMod
2. Make sure you're in Package Mode
3. Click on the big folder button, and select Guild Wars as your target application
4. Download all the TexMod files (.tpf) that you want to run
5. Click on the small folder button by the Select Packages box and hit Browse
6. Find the .tpf files you downloaded and select them one at a time
7. Hit Run and you'll have your modified Guild Wars game.
My thoughts are to not stop at just Cartography assistance. Right now I'm running In Game Mission Maps, Hi Res Skill Icons, Modified Hero Flags, and one of two user interface mods: either Glazed Graphite or Dark Glass. Publicly released and tested TexMod files can be found here:
http://wiki.guildwars.com/wiki/Guide_to_modifying_in-game_graphics/Player_made_modifications
Good luck and enjoy!