This isn't the full song...but I'll show you the lyrics...
한눈 팔지마 누가 뭐래도 내꺼 (내꺼)
han-nun pal-ji-ma nu-ga mwo-rae-do nae-kkeo (nae-kko)
다른 여자랑 말도 섞지마 난 니꺼 (난 니꺼)
da-reun yeo-ja-rang mal-do seokk-ji-ma nan ni-kkeo (nan ni-kkeo)
새끼 손가락 걸고 꼭 약속해줘요
sae-kki son-ka-rak geol-go kkok yak-sok-hae-jwo-yo
절대 나 혼자 내버려 두지 않기로
jeol-dae na hon-ja nae-beo-ryeo du-ji anh-ki-ro
1더하기1은 귀요미
il-deo-ha-gi ir-eun gwi-yo-mi
2더하기2는 귀요미
i-deo-ha-gi i-neun gwi-yo-mi
3더하기3은 귀요미
sam-deo-ha-gi sam-eun gwi-yo-mi
귀귀 귀요미 귀귀 귀요미
gwi-gwi gwi-yo-mi gwi-gwi gwi-yo-mi
4더하기4도 귀요미
sa-deo-ha-gi sa-do gwi-yo-mi
5더하기5도 귀요미
o-deo-ha-gi o-do gwi-yo-mi
6더하기6은 쪽쪽쪽쪽쪽쪽 귀요미
yuk-deo-ha-gi yuk-eun jjok jjok jjok jjok jjok jjok gwi-yo-mi
난 귀요미
nan gwi-yo-mi
It's not that hard one the first part she says 1+1=Little Cutie...
Put up one finger then the other and then twist them on your cheek or in front of you.
2+2= Little Cutie
Do the same this like the first one except you do bunny ears.
3+3= Little Cutie
You can either do rotation or what Eren did.
4+4= Little Cutie
You press your fingers together and make a diamond or what Levi/Eren did.
5+5= Little Cutie
You stick up your whole hand then the other and you clench and unclench your hands. That's how I do it.
6+6= Little Cutie
Stick up one hand and use the other but just one finger and kiss the tip of each finger quickly and say 'Gwiyomi!'