I have a 10" Skywatcher Dob and with a 25mm EP your view of jupiter should be about the size of the picture below and the longer you focus your eyes on Jupiter the more detail you will see.
Is the 25mm the only EP you received usually you get 2 or 3 with a new scope.
I agree with Leon you should be able to make out some detail remembering that the longer you look at it the more you will see.
Is the 25mm the only one provided with the scope this would surprise me as usually you get 2 or 3 EP's with a new scope.
And using a barlow lens increases the size of the object you are viewing but increasing the power you use can make the view worse if conditions are not ideal.
Collimation could be and issue to but if it is a new scope it should have been collimated for you before you got it.
You need to get together with a local group of astronomers to help you out in the beginning as you will feel like a fish out of water I know I did and having others to talk to and to see what views look like through their scopes helped heaps.
Anyhow welcome to IIS heaps of helpful people here and I am sure that someone close to you will offer to get you started.
