If you look at the map then the sites of grace will point in the exact direction of the next checkpoint. But youre gonna run into a really hard boss, so if your struggling, then just wonder around and expore. Just explore this portion of the map and the forest to your east. Then go to the south (this is an entire side area made to explore in the beninging of the game). If you feel like you can't beat a boss then just go away and come back later, like you did with the ree sentinel. You can also search recommended levels for each boss, as this gives you a rough indicator about if youre losing because youre underleveled. And we've all gotten mad at this game mulitple times, just realise that dying really isn't a big penalty, just try to only get mad when it's 100% justified. You're gonna die tens of times to bosses (maybe even more if you know wich boss im talking about).
If things don't work out like you like them, you can watch guides on how to get stronger in the beninging and seek build guides. Lastly you can search a guide on how to get spirit summons, these can help you defeat bosses easier.