Swapping starters in Pokemon SoulSilver

[BNSaturday]

Hey, everyone! I'm relatively new to the world of save editing (all I've ever done is generate some competitive teams back in Gen 6 when it was as easy as scanning a QR code), so please be a little patient with me.

I'm trying to figure out a way to swap my starter in Pokemon SoulSilver from a level 5 Cyndaquil to a level 5 Chimchar. I have PkHex running on my laptop, but after several minutes of browsing around my 3DS's SD Card and trying to find tutorials both here and and in other places online, I can't seem to figure out how to use it to edit my SoulSilver save data. How would I go about doing this? Any advice you can give is appreciated.

Note: I have literally no hardware other than my 3DS and laptop, so if I need more stuff, I'm probably crap out of luck.