CosB        cosB
--------  +  ---------     = 2secB
1+sinB     1-sinB

Adding those in the left side of the equation you get,
 \frac{2cosB}{1- sin^2 B} = 2secB
 \frac{2}{cosB} = 2secB

remember sec(x) = 1/cos(x) therefore,

2secB = 2secB

Remember to only keep working on one side of the equation for proving. There are a lot of sample problems on the internet that you can work on to get better not just for this topic, but for other math topics as well. Try, edX, and coursera to learn more haha