I guess you guys already know how to say these expressions in Japanese:
-Nice to meet you. はじめまして/hajimemashite/
-I'm... わたしは/watashi wa.../
-Thank you. ありがとう（ございます）/arigatou (gozaimasu)/
You can check some common greetings in this post, too:
<Common Greeting Phrases in Japanese>
There're tons of resources about self introduction in Japanese. They tell you how to say where you from, what you do, what you like, etc. I want to add some expressions to your self-introduction list.
(1) I just started learning Japanese.
/nihongo no benkyou wo hajimeta bakari desu/
Or make it more simple --> I'm a beginner.
(2) I can't read or write Hiragana/Katakana yet.
/mada hiragana to katakana ga wakarimasen/
Simple version --> I don't know the characters yet.
/mada moji ga wakarimasen/
(3) Can you help me with learning Japanese?
/nihongo no benkyou wo tetsudatte kudasai/
Simple version --> Can you help me please?
/tetsudatte morae masu ka?/
Now you can speak Japanese! ;)
Here's an idea for Language Exchange: What Should I Talk About?
Try it, and please don't afraid of making a mistake. If you have any questions or comments, I'll be happy to hear them! Or, why don't you try writing your self introduction here? ;)