There are many ways to skin a cat.

Which model Mackie are we talking about?

Here's my 2 cents.
You could do a couple of things with this set up.

That console has Tape sends and returns. It's a little deceiving when you look at the back of the desk. It will have 24 tape sends, which are all coming from your 8 buses ie; tape send 1-8 are sent via buses 1-8, tape sends 9-16, are also sent from bus 1-8. and so on.
So, you could use your 8 buses to send into the 8 inputs on your digi02. then you can return into the first 8 tape returns on your console. There's a Tape / Line switch at the top of each strip on the console which will route either Tape or Mic/Line to the fader, or the inline knob, so you can have basically 2 inputs per strip as this is an inline desk.

Another way would be to use the console like a split desk. You can use say the last 8 inputs on the desk as mic pre's and wire the direct outputs of those channels into your Digi02, then bring the outputs of the digi02 back into say the first 8 inputs on your desk.

The last thing to consider is that you are using a Mackie. You may want to just mix in the box, as the quality of the console is not such that you will really benefit from returning the 8 outputs of your digi02, unless you have some smoking outboard comps / eq's / effects. So you may be better off just using a couple of channels to monitor through.

Hope this long convoluted answer helps!!!

Drstudio explained the tape/Line function, but don't forget
The 8 bus also has the direct outs on each strip. I use both the tape sends and the direct outs. If I have more than 8 tracks to record at once I use the direct outs.

The Mackie 8 bus board adds a 'colour' to the sound, if you like that sound great! If you don't then you may want to consider mixing in the box.
Typically I use mine if I have too, otherwise I use discrete pre-amps.

Have Fun!