I am new to this form, and I am in no way knowledgeable about vehicles

I have a 2006 Colorado Crew Cab. I just ordered a BAKflip G2 tonneau cover for it. The installation is no-drill & I've seen a video online & read installation instructions online. Looks pretty simple to do! But....

There are 2 drain tubes. It says it can be installed over any type of liner, but I don't know where & how I would install the drain tubes in mine. The liner is a hard plastic (I guess?), I think you call it a drop in. The only holes in the liner are the 2 in each corner for tie downs.

Can anyone explain what I will need to do, please?

I don't expect to receive the tonneau for 1 to 2 weeks. I can take pictures of the bed of my truck if needed. Just let me know what views will be needed & I can get them tomorrow during daylight

Thank you!!
Sandy