I tried to convert a test nem account to multisig, but how do I upload the private key? Do I just copy from text edit file the code?
Thanks,
CCC
You should put private key as plain text.
Go to Account in top navigation, in private key section provide password and click plus button.
You should have this backuped for mainnet account 
Yes, I have the .wlt file but it’s not converting into a multisign account for some reason.
What do you put in private key field? It shouldn’t be content of your wlt file. It should be private key which is 64 signs length.