Inserting the graphics:
1) Make sure there are no unsaved changes to your ROM.
2) Go to File -> Compression...
3) Put the address of your compressed packet in the address field. (38000)
4) In filename, press the "..." button and select a destination.
5) Press Compress.
6) Compare the compressed size on the status bar to the compressed size you noted earlier. If it's the same or less, save. If not, note the size, reopen your ROM, and proceed to Finding new space.
Finding new space:
1) If you don't have it already, download the
Chrono Trigger Database.
2) Look for free space or JUNK greater than or equal to the compressed size. Temporal Flux will take this space starting from the beginning of the ROM when saving changes.
3) Go to Window -> Custom Data.
4) Add a new entry for your packet. Set start offset and end offset to the size you need, and override free space to true.
5) If there's a message at the bottom that says Warning - Space Requested In Use, try again with a different address. If not, insert the modified graphics at that address.
6) In a hex editor, go to 0x027220. Take the last two byte of the address, and insert them in reverse order. Using 0x38000 as an example, you'd take the 8000, and insert them as 00 80.
7) Go to 0x2738C. Take the first byte of the address, add 0xC0, and store it here. In this example, you'd take the 03, and add 0xC0 to get 0xC3.
After this you'll need to change the Dark Ages tile assembly. This is at 0x3EE464-0x3EE56. Every fourth byte will be the tile index.
Tile Molester's Tile Grid can help with this. The row followed by the column will be the index you need. For example, "dd" in Middle would be 5A. 00 can be used for a blank tile if your text is shorter.