You have several options:
Most DIY vessels come with a 3/4" female screw thread. You could simply fit a 3/4" male screw to 1/2" hose barb to either side and then your 1/2" hose could jubilee clip on.
Most suppliers send DI vessels out complete with male hoselock on either side of the DI. This means you would need to attach female hoselock fittings to your 1/2" hose.
Another option is to fit 1/2" female John Guest fittings to the DI and then fit 1/2" barb to 1/2" male John Guest to your 1/2" hose and then they'll simply push together.