You have to do nothing! Simply stay online with the client and the wallet unlocked, and you will eventually find a Proof of Stake block if you have enough mature coins in your wallet."
Staking guide says you need to stay online in order to get reward.
With PoB I didn't find any info about staying online. It looks like you can burn coins and they'll be fining blocks with the wallet closed.
In order to find a block - either PoB or PoS - you must be online. It would not make sense to reward nodes that are offline because they would not contribute to blockchain maintenance & security.
The point with PoS is that there is a yearly limit for the PoS coins you can earn (10% of your stake/year, that means about 0.3% for every day the stake has not moved). That limit is fix, it isn't increased if you mint more often during the year. So in theory you can just wait until your coins have "matured", then connect the wallet (unlocked), mint a while and eventually (if you have enough stake and there are few competitors online, pretty fast) you will find a PoS block. You then can turn off the wallet again for some weeks and wait again until your coins are matured again.
However, for the health of the network the "ideal situation" is if everyone mines 24/7, so if you can, you should. Attacks are less likely then.
With PoB, in contrast, you have more chances to find blocks if you are online 24/7, because you compete for the reward every time and the reward is not limited. That's why PoB is a great measure to incentive 24/7 participation from nodes and provides stability.
PS: Nice price evolution, Slimcoin's market cap (if we take the ask or "last" price of 1990 satoshis) has hit a new high of ~880.000 USD, almost a million! However, I am a little bit worried if this pump "to the million" doesn't come a little bit too early.