I am assuming you mean the client (like tcpGecko.NET)
You will want to select the 10 range ( 0x10000000 - 0x45000000 ). This is where the codes live in most cases. I have seen some go lower and some go higher - but going higher than 0x45000000 causes errors in almost every case.
If you are searching - that is you search range.
If you are in the memory viewer that is the range of memory you are viewing.
In either case - once you find an address (or confirm an address for a code you have works) you will need to poke the value, of that code into memory, at that address.
JGeckoU also works for memory editing (code handler does not function on loadiine and loadiine has different offsets for the codes than retail - and even a new nightly builds can affect that offset) and hopefully soon there will be searching implemented.
Also, if you like python, pyGecko is pretty neat.
Sorry left out an important link - there is a lot of info about all of this stuff here
https://gbatemp.net/threads/post-your-wiiu-cheat-codes-here.395443/