It's straight forward. It could still be a faulty GPU.
Effectively just ensure that you lower the GPU into the PCI slot evenly until you hear the latch click into place. Then secure the GPU to the case. If any GPU requires additional power connectors, then plug them in accordingly. Ensure you connect your monitor directly into the GPU and not the Onboard graphics.
- Also take all necessary precautions when touching components, such as static discharge etc. -