First, you need to get the denominators (the bottom number) the same. The smallest number to get them to is 15.
So, what you need to do is take 2/5 and multiply the bottom by 3 to get 15, and since you did it to the bottom, you need to do it to the top too. So you would get, 6/15.
Then, for 1/3, take the bottom number and multiply it by 5. Then, since you did it to the bottom, do it to the top as well. You would get 5/15.
Then, you need to put them side by side. You don't add the bottom, so your denominator would remain 15, but your numerator (top) would get added.
6 + 5 = 11
15 15 15