What Is Nolus Swap?
Swap is not part of the Solana app. In a Solflare or Phantom session there is no Swap button in the Account popover and no Swap tab in the transfer dialog, so decide which asset you want to hold before you fund your Nolus account. Convert in your own Solana wallet and bring the asset in with Fund. See Swap Assets.
This does not affect margin positions. When you open, repay or close one, the protocol makes the conversion itself, which is not something you trigger anywhere in the app.