Head over to https://claim.balancer.finance/ to claim your BAL from liquidity mining.
BAL tokens for liquidity mining of any given week will be available to be claimed the following Tuesday evening (EST time).
This claiming mechanism will allow you to choose if you want to claim on a weekly basis or accrue and claim at a later date. At this time, BAL earned through liquidity mining does not expire, so you can take your time to claim them. If for some reason this changes in the future, everyone will be notified well in advance.