Hey there RoastedZucchini,
Thanks for reaching out to Apple Support Communities. I understand you’re unable to use Memoji stickers on your iPhone 6s. I’ll be happy to help with this.
Have you attempted to create a Memoji sticker yet? If not, do that first using the steps from this link:
How to use Memoji on your iPhone or iPad Pro
Once you do that, see if you can use them as a sticker as seen in this article:
Use stickers with iMessage on your iPhone, iPad, and iPod touch
If you still don’t see Memoji stickers, make sure you have them set to show in the app drawer. Take a look at this link for more info:
Use iMessage apps on your iPhone, iPad, and iPod touch
Let me know if this resolves the issue for you.
Take care.