You can't get admission in MCA through GATE. GATE is for Master’s programs and direct Doctoral programs in Engineering/Technology/Architecture.

For MCA, You can appear for NIMCET exam to get admission in NITs and there are several other university level and state level MCA entrances for which you can fill form.

MCA Entrance exams:

NIMCET

BIT MCA (For BIT, Mesra)
JNU MCA ( For JNU, Delhi)
Pune University MCA
BHU MCA (Banaras Hindu University)