How to suppose the current directions for KCL?
Question statement is a little hazy, but the general idea is, current entering a node gets a positive sign, current leaving a node gets a negative sign, and the sum of all of them comes to zero.

One way to assign currents is to recognize that current flows around the loops. So for each loop, you name a variable for the current. Then it should be straightforward to enumerate the currents entering and leaving a node.