Since the denominators aren't the same, you need to find the LCM. So the lowest Common denominator. Similar to finding factors. You need to find a number that will go into both the denominators, which in your case, is 6 and 8. The lowest would be 24. Both 6 and 8 can go into 24, right? 6 * 4 = 24 AND 8 * 3 = 24?
Ill show you ONE way of displaying your work, this should be an easier way.
1/6 + 1/8
LCM = 24
24(1/4) + 24(1/8)
To work this out, you need to multiply the 24 to the numerator, which is 1. Then multiply the resultant to the denominator which is 4. So you'll get 6. Do the same method with the other fraction.
Working
(24*1)/4 = 6 [1]
(24*1)/8 = 3 [2]
Then add the two together.
6 + 3 = 9/24 [the LCM will be in your final answer]
From here you have to see if you can simplify this any further. In your case, You cant, so this will be your answer.
Also, make sure you look up the exponent laws and multiplication rules, this should help you a lot :)
I really do hope you followed through.