Assuming it is text and not graphics
Four main things, though arguably three.
1) Use spaces and hope it goes across.
2) Use spaces and just make it in the middle.
2a) I don't know what causes a new line in that (whether it is auto wrapping or manually new lined) but you might be able to fit a bit more in, and maybe jiggle the words a bit to fit lines.
For both of these then fitting everything in and memory issues tend to arise. That said difficulty is basic text hacking.
3) You get to play assembly hacker with the position of the text layer (don't know if it will be sprite or BG, BG tends to be traditional one but a few intro scenes to an action game might be sprites)
4) You play assembly hacker but find it is one of those games that sets an initial position and works from that for the subsequent lines. Bit easier than making it do a new location calculation for every line if so, I note it here just so you are thinking of it as a possibility when you are playing assembly hacker.
The SMS graphics are handled by the VDPhttps://www.smspower.org/uploads/Development/msvdp-20021112.txt
Found on https://www.smspower.org/Development/Documents
Probably start by figuring out what mode it is and then how to manipulate it to do what you want. There are some combined text and graphics options so I would lean towards those.