The first time you buy ETF, you have to approve the token. This gives the DeETF app permission to swap that token from your wallet.
Once you approve a token, you will not have to to approve that token again on the DeETF app until the approval mount is exhausted. A one-time approval is required for each ETF you wish to buy.
When buying etfs on DeETF, you will see the following message:
Once you select the Approval icon you can proceed to buy your etfs.
When you approve a token, it is considered a transaction so you will have to pay a network fee.