You are setting up a Reward - that means you are going to give a Task user some exchange for their tokens. It could be a voucher, money or other rewards you will allow them to redeem.
What wallet address to use?
If it is you who are providing the reward for tokens, you probably want the tokens to be sent to your account wallet, as it is an easy way for you to verify you got sent the funds before you provide the reward.
Another option can be to send tokens to a "Burn" address. A Burn wallet is a Stellar account that does not have a private key - which means any tokens sent to it are effectively destroyed and can't be used.