Errors with setting up payment and delivery option and adress

[The_Duke]

Hello there guys, i have a problem with virtue mart 2.6.0. Everything works just fine, i created a product that i want to sell, but I dont see where to choose to have add to cart? Where is that in settings?
And one of my friends added me that, but every time when i wanted to add something into cart i got several errors:
Cannot find tslib/. Please set path by defining $configured_tslib_path in checkout.
Cannot find tslib/. Please set path by defining $configured_tslib_path in cart.
And, now i cant choose good adress cart... :
Cannot find tslib/. Please set path by defining $configured_tslib_path in editaddresscartBT.

Can anyone please help me with this?
P.S. I dont have 'Add to cart' now