T- Shirt Mock Up adobe illustrator

[Sam_117]

Hi I was wondering if anyone could help me TIA. 
I'm new to adobe illustrator and I'm trying to make designs for T-Shirts etc. and apply them to mockups. I downloaded a pre-made vector shirt with mesh lines from shutterstock and I'm trying to apply different kinds of designs that blend with the mesh lines. I've tried clipping mask and opacity masks etc. but they don't seem to blend correctly, I'm probably missing something but I'm unsure. Any help is greatly appreciated thank you. 

[Doug A Roberts]

Please show an example with layers visible and explain what you mean by 'blend', which can have a few specific meanings in the context of Illustrator.

[Sam_117]

Sorry I apologise for my lack of knowledge for terms. 

 In this Example I'm trying to apply this pattern to both the left and right side of the chest. I want the pattern to bend with the mesh lines, so it appears 3 dimensional.

Thank you for your time. 

[Monika Gause · Accepted solution]

You can copy the gradient mesh and then put your design in place on the shirt. Past the gradient mesh in front and then select your design and the gradient mesh and Object > Envelope > Make with top object.