You've got to insert the new palettes with a palette editor for example, and then add them to the overworld palette table. That table is located at 0x3A5158 or, if you use JPAN's patch, 0x1A2400. However, unless the latter applies, you'll have to repoint that overworld palette table to free space before you can add any palettes. Each entry in that table has the format PPPPPPPP TTTT0000, PPPPPPPP being the pointer to your palette, and TTTT being a unique palette tag of your choice. It must not be 0x11FF however, as this marks the end of the table. You can consult the instruction manual of JPAN's patch for further information. When you've added your palettes, you need to make your overworlds use them by selecting the palette tag you chose (in this picture it's where it says 0x1106).