In the Define menu choose Injectionsand choose Create :

By clicking on the Ceate button, you open the SetInjection Properties window. In this window, you can set the properties of the particles injected in the continuous phase.

1.    Choose the injection type from  :  single or group.
            If you choose singlego to step 2.
            If you choose group set the Number of Particle Streams and go to step 2.
2.    Choose  the particle type Inert.
3.    Choose the Material in the material list.
4.    Set the PointProperties (this step define the point from where the particles are injected in the continuous phase flow and the conditions of the injection).