The first thing to do is to obtain the proper sealant, look at the brand of your gutter if it has a name then you can that manufacturer might have some sealant which works best with their particular gutters.
Cleaning the Gutter
The 2nd steps to fixing your gutter leak is to clean the gutter, get rid of any excess water and clean any dirt or other unwanted materials, afterwards remember to dry the gutter out with just an ordinary towel or rag use washing up liquid or just ordinary soap to get rid of all the surrounding dirt.
Use the Sealant
Next add the sealant to the crack within the gutter, after you have added this use a simple paint brush to move it around the cracked section, ensure the sealant sticks really well before you leave it to dry.
Check the Leak
Poor some water a period of time after you applied the sealant (check manufacturer’s instructions) and then pour little bursts of water into the gutter to see if the problem has been fixed.