You're welcome! Depending on the situation (formal, casual, etc.), you can reply to the group or the individual who added you in a few different ways.
Official Reactions
These are suitable for work groups, professional environments, or situations when you don't know the individuals well:
"I appreciate the gracious welcome and look forward to contributing to the team."
"I appreciate the chance to join this organization. Being here is an honor for me.
"I appreciate you including me. I'm excited to share and learn from you all."
"I'm delighted to join the team and am excited about the potential opportunities for collaboration."
Informal Reactions
These are excellent for casual communities, families, and social
Teacher Group Names:
I appreciate you including me in your group. I'm really glad to be here.
"Hi everyone, I appreciate the advertisement! I'm excited to get to know each of you."
"I appreciate the welcome! I'm glad you're here. Please feel free to share anything.
Thank you for the invitation! This group seems like a lot of fun.
A straightforward "Thank you" or "Thanks!" is frequently also quite appropriate.