Unzip/extract the zip file which you have downloaded
Then, Copy all contents of the "upload" directory into the root folder of your opencart installation. Note: Do not copy the upload folder itself, just the files & directories inside.
You need to install vqmod extension for this module. You can download vqmod extension from this url here.
After installing vqmod extension, go to the root of your opencart installation.
Place redeal.xml file into "vqmod/xml" folder. (redeal.xml file is available in module zip file downloaded in step 1)
Then, Go to admin panel of your Opencart 1.5 store
Go to the "Extension->Modules" from top menu. See below image:
If redeal module is properly installed, then It will display in modules list here:
Click on Install to install redeal module here:
After configuration of the module, you can place order in your opencart store and check Redeal popup on thank you/order confirmation page in order confirmation page.