Use the 3" putty knife to scoop up the pre-mixed joint compound and apply liberally along the mesh tape, working the joint compound through the mesh holes and completely filling the gaps along the wallboard edges. Pic 1.

Continue working your way along each cut line, smoothing the joint compound along over the top of the mesh tape to cover it completely, both lengthwise and side to side. Pic 2.

You may have to hold one end of the mesh in place occasionally, if it wants to start sliding along with the movements of your putty knife.