I'm sure this will be simple enough.
Requirements:
9.x-9.5.0-22 3DS
No exceptions.
At least 150Mb of free space on SD card
Hex editor on PC
1. Open game on 3DS.
2. Go to your 3DS browser without closing the game
3. Clear cookies and history on the 3DS browser in settings (If this doesn't work click on Initialize Save Data)
4. Go to this link
http://lunarcookies.github.io/fcram.html not working atm. Use
duke_srg's page instead. Open the page and choose "FCRAM dump", (not "memory dump") write a file name and press launch.
5. It will flash black and white for a few minutes and will finally crash the browser.
6. Put the SD card into your PC
7. Open FCRAM with hex editor.
8. Find the value in
hexadecimal. (It is endian. So example if you were to separate hex into bytes AB CD EF you would reverse it to EF CD AB. Also if you get an odd amount of numbers in hex just add a 0. example: A BC DE will become DE BC 0A.)
9. If there's only 1 result, lucky you!
Copy the offset/address on the left (will always end with a 0 so remember to add the number/letter at the end like in the image)
10. Open
http://lunarcookies.github.io/cheat.html, (this one still works) (credits to
MegaSynka for both lunarcookies links) paste the address/offset in. Separate with a space, and put the amount you want the value to change to in hexadecimal example: 000F18A5(no need to reverse it this time) Value must always be 8 characters or it won't work. Once you're done click "QR Gen" and leave the page open
11. Done. Open the game, go back to home menu, L+R, turn on the QR scanner on 3DS and scan the generated QR code from your PC.
(Thanks to
duke_srg for reminding me about binless versions

)
Feel free to ask questions
You can ignore the next parts if you want to, it'll likely confuse you because of my bad english
If you have small numbers, dump the memory 1 time, change the value in-game, dump again, change again, dump again, repeat until satisfied (3-4 times is usually all you need) Open cheat engine, open the first FCRAM, search with array of byte (and don't forget to reverse the value) first scan, open the next file, insert second value, next scan, repeat until you're satisfied.
If you're only going to use 2 bytes, in your offset replace the first 0 with a 1. value would be like this 0000AB43. If you're only going to use a byte, replace first 0 with a 2. example value: 000000AB.
Alternatively, if you don't want to visit multiple links, you can go to duke_srg's website
http://dukesrg.no-ip.org/3ds/rop.html
It has everything Spider uses.
Just choose a mode from the list and fill in the textbox. You can make a QR code with it or launch it directly from the 3DS too!
I went up and read the arcode documentation and there's a better way of changing 1 byte. You can change the first number in the address to 2 and just put a 0's followed by a 14. So it would be 20895A34 00000014
Dunno what's the 2nd line though. I'm too lazy to check lol