Hi I am new to this site and new to astronomy!!

I have a skywatcher dob goto 10" and have had it for 3 weeks. I am having trouble focusing with a barlow lens attached to a 10mm. I can find the object such as Jupiter ok but as soon as I attach the barlow I am unable to get any focus, it is just one big blurry object! Does anyone out there have the same scope as me and has anyone had similiar issues?
Also I am having trouble slewing to an ojbect accurately with the goto. It will go to the general direction but then I have to try and refine the search. Any solutions?
Thank you ....