Is there a way to select that the card I want to add to my inventory is a foil card?
I have a Captain Sisay and the value shows as if it was not a foil.. how can I get the foil price to show in my inventory?

1) On your inventory page if you mouse-over the card you want to edit there will be an Edit button to the right. Clicking on that Edit button will popup a small dialog.
2) On the right side of this dialog is a gear icon. Click that icon.
3) Select the Foiled option.
4) Click Done.
5) Click Apply.

Alternatively, when you are adding cards via the import feature, you can skip step 1 as the most recently added card will be displayed at the top and you can edit the characteristics there.

Thank you so much this was really helpful!:D

No problem. Glad I could help :)