with Bard, it's pretty difficult to know when you need to leave lane and go get your chimes.
personally, level 4 is the perfect time to go (only if your ADC is pushing), at the same time I place a deep ward in their side and go back to lane.

Bard is a roaming support, its pretty simple to roam, but be careful to not let you ADC alone too long..

Now, about how to attacks and engage with Bardo.
Bard can deal big big damages by his meeps (magic damages) that's why more chimes you have, more meeps you get and more powerful they will be. at a certain amount of chimes (15), your meeps will deal area damages that slow ennemies.

To engage a fight, 2 options can be taken.
Engage with your Q ( your Q needs to be really setted up) to stun ennemies and fight
Or engage with your ult (generally, you engage like this when you're with all your team or when your jungler gank your lane).

Bard's ult is a real game changer.
you can stasis literally EVERYTHING on the map. Drakes, minions,herald,tower,flowers... EVERYTHING.

Here's some tips you can do with your ult.

Tower diving an ennemy: you can put the ennemy turret in stasis, and go get your kill very safely.

Heralds are literally useless when there's a Bard in the game. When the herald prepare to dash, put your turret in stasis and boom ! Herald canceled

Pretty difficult to do but when there's an low HP ennemy under your turret who's trying to get plates, put their minions in stasis, the turret will focus him and die.

there's more and more things to do with Bard's ult... Let your imagination and skill free !

thanks to have read this.. I'm a really big Bard fan and OTP.. I think he's the best and funniest champion in the game..

Enjoy Bardo Bardo !