When sending messages, I find it works best if you have at least had some kind of conversation with them before -- however they do NOT need to be someone you have a strong relationship with. Sometimes I get the best results from people that only know me through Facebook. Keep it simple - but you can make it conversational:
Hey Susie! Hope you aren't getting too crazy being stuck at home with kids with this virus thing going around ... and I wanted to ask ya too - I'm just curious, would you like to be my beauty affiliate of the week?
The most important things is that you keep it short, you DON’T explain what that means or that they can earn anything, and you END with a QUESTION :)