You have to keep your 5k AKA on your masternode wallet for it to work, just send the surplus to another address on wich you will build your 2nd masternode when you'll get 5k on it.
How can I guarantee the coins left is the right 5k though? I can't see any options for coin control (picking sources of coins to send) or does the node just "see" the 5k and that's all that counts? Other MN coins I have allow you to lock out the coins for a node and only send from the pool of coins unrelated to your MN. It's not exactly a hardship to set up nodes just seems a little backwards compared to other coins.
Your MN is tied to a wallet address, just check your wallet here:
https://explorer.akroma.io/Then you can create another address and send AKA on it with
https://w.akroma.io/