The first conditional (also called conditional type 1) is a structure used for talking about possibilities in the present or in the future.
This page will explain how the first conditional is formed, and when to use it. You will also find some exercises
Second Conditional: http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/2cond2.htm
Third Conditional: http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/3cond1.htm