Hi Gavindale,
The only existing walkthrough for Ember is at https://www.supercheats.com/ember/walkthrough/
1. About skills and special abilities:
They show as small icons under the picture of each team member. To use them you you click on the icon. For some
of them you you need to drag the icon towards the enemy that you want to hit.
2. Healing potions.
I suppose that you are still in the barrows - there you don't really need them because you can find a bedroll with
a nearby explanation text that will allow you to heal completely just by using the bedroll.
3. Spider Queen.
Depending on your preferences you can equip your chars in 2 ways in the Barrows:
- either your Lightbringer as a melee fighter and Coren as a marksman - this is what the walkthrough does
- or your Lightbringer as a wizard and Coren as a melee fighter
In any case you give the best armor and weapons to the melee fighter and send him forward while the ranged fighter
(marksman or wizard) stays behind and uses his ranged weapon.
The Spider Queen is not too much of a problem if you concentrate first on her and then on the spiderlings.
4. Anything of good use.
To get a first idea of the game you can set your difficulty at "easy" via the menu item "Options". You can change
that at any time.

Hope that helps.
Rudi

Instead of opening a new thread I just jump in here:
Is there a way that my companion can use potions? No matter what and how I try, only my main character uses potions, my companion seems to refuse to getting healed by potions. He doesn`t drink them even when I select him and try to drink it then. It`s always my main character who uses them.
Or is there a manual for the game?

In case you haven't found an answer yet, and to leave an answer for anyone who may land here... There are two ways:
1) If you put potions (or other consumables) in your quick slots (three circles a bit to the right at the bottom of the screen), when you click on them to use them you'll see small icons of your characters pop up just about the item, and you can click on the character you want to consume it.
2) From your inventory, you can drag an item to one of your party members' portraits for that character to use it.

Hope this helps!