I'm leased some Waves. I can see there are some amount of Incoming Transfer in transaction history, but the incoming transfer amount is not updated in my balance.

First of all, the LPOS reward depends on the conditions of your pool. Please find out more info from your LPOS pool.

Each asset is always available in the Portfolio tab section. 

Also, there you can check the DETAILS or TRANSFER your assets.

Here you can trade them, check tutorial - How to trade tokens on the DEX