simple intensity map from excel table

Dear all

I just began using matlab and i need to make a simple intensity maps from an excel with 3 columns (x ,y , intensity). I browse a bit around and i found options like colormap and imagesc but i think i am missing something in the process. So i guess the process is like creating some variables like lets say a= x values , b=y values and c= intensity values and then colormap (a,b,c) ? I can say i am a bit confused. Could you help me with the line of commands?

Thank you in advance!