No, you just need to stake them once.
You receive both APY from the vaults and pool rewards.
Your voting weight decreases over time but your boost will take notice of your decreasing voting power at certain checkpoints like withdrawing or staking. For example if you start at 1000 veRBN and your voting power decreases to 800 veRBN, your boost will still use your original voting power of 1000 veRBN until a user checkpoint.
After creating or adding to your lock, you need to click the "Apply Boost" button on each gauge you're providing liquidity in to apply the boost. Your boost can also be updated by depositing and withdrawing from a gauge as well as claiming RBN.