Electron Cash SLP - Check One Token per Address
Download Electron Cash SLP here (simpleledger.cash)
You can see your tokens in tokens tab of EC
Go to Addresses tab and find the address where you have NFT.
You can view these addresses in explorer and make sure you have a single token on them for swapping.
If you do not see Addresses tab, you can enable it from View -> Show Addresses.
When you find the address, right-click on the desired address and then select private key. Enter the password you previously set.
Now you see your private key. You can use it to sign your swap at the NFT DEX
Why we require a new legacy address for swapping?
Swap addresses are special because they change from containing a SLP NFT token to containing BCH coins. Using a new legacy addr helps to keep them separate from regular use wallets. Yet make it easy to import or sweep, once the swap has been completed.
Alternatively, use an addr from EC-SLP enabling "show coins". Each coin has an independent private key that you can use to store single tokens and sign swaps.