I'm going to give back to the community now, since it's been so good to me. I personally like NSC Builder, you can easily google it, it's created by julesontheroad. Download it to your pc, extract it, and run the batch file. Do the following:
- Choose Multipack mode
- Drop your first nsp file your game file into the window [Hit Enter]
- Drop your second update file into the window [Hit Enter]
- Choose to Process those files
- Tell it what output you want XCI, NSP etc
- Patch firmware required if you want
- Merge all
- Install
Done.