How do you do a join on two tables when you are implementing uows & a generic repository

My unit of work is basically set up as this tutorial, with minor additions:

http://www.asp.net/mvc/overview/older-versions/getting-started-with-ef-5-using-mvc-4/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application

I want to know how to do a join on two tables. I tried adding this to GenericRepository, but as you may guess my Linq knowledge is dubious.

public virtual IQueryable AsQueryable()
        {
            IQueryable<TEntity> query = dbSet;
            return query;
        }

And then doing

// uow is defined as new UnitOfWork() on class instantiation
var data = from x in uow.MyRepository.AsQueryable() 
           join y in uow.MyOtherRepository.AsQueryable() 
           on x.prop1 equals y.prop2

But it wont let me access properties within my table. I basically need a way of returning the table as a queriable entity (I think)