Hola?!

[Fcelss]

Hola! Yo soy el Mark. El pelotas son pequenas.

Hi I'm Mark, I'm learning Spanish with Rosetta and Rocket Spanish. Wassup!

[Rusty]

Hi Mark.
¡Bienvenido a los foros!

The correct way to say "I'm Mark" is "Soy Mark."
The last sentence you wrote needs to begin with a different article (the article agrees in number and gender with the noun).
There is an "Accent" pull-down menu above the text input area that contains all the special characters you'll need to use when typing in Spanish, like the upside-down exclamation point or the ñ in pequeñas.

Do you know what your last sentence means?!? Perhaps you don't want to put that in your introduction. :D

[JPablo]

¡Bienvenido Mark! :)

Seguir los consejos de Rusty compensa...
[To follow Rusty's advices pays off...]

At any rate, enjoy your practice and learning around here!

[CrOtALiTo]

Hello Mark

I bid you welcome to these forums, please don't hesitate to ask us your questions.

Sending any question is the best sometimes.

[Jessica]

welcome Mark