Intel and AMD include thermal paste on the bottom of their CPU coolers as do some after market coolers. The A30 does not and comes with a tube of thermal paste. In most cases, you want to clean the old stuff off of the CPU using at least 90% Iso propyl alcohol, preferably the higher % the better. Once clean you will want to apply a small amount in the center of the CPU, typically the size of a small pea.
When you apply the heatsink you want to apply even pressure which will spread it out over the CPU and it even helps to slightly twist the cooler to the left and right very slightly to help it spread.
With this one, make sure the fan faces the front of the system. I am not familiar with it and I know in some cases with the AMD clip system it might not be possible but try. If not that's fine but it wont be nearly as efficient as it could be which is why I prefer to get coolers that come with back plates and I like Intels system a bit better as you can mount the fan for better efficiency.
Good luck and remember, a small amount of thermal paste. Too much will saturate the CPU and cause it to leak out to the sides, possibly causing shorts and as well will make the cooler not run efficiently.