Kaimashita Can someone please explain what is "Kaimashita" and when/how to use it?

Introduction Hajimemashite! Namae wa Noor desu. Yoroshiku onegai shimasu. Ikaga desu ka? Basically, at this point, it's definitely hard for me to build up sentences as I'm still struggling with the particles, Japanese words and stuff so probably it will take me a while before I KNOW how to build sentences. HAHA! For now, I think I'm quite happy with memorizing and understanding these lines. ;) Sayonara!