Well installing a style is more or less the same as installing the software.
Upload the relevant files to the server, import the style, set any configuration (e.g. image path) as necessary, although the last step isn't required if you upload the files to the correct directory as specified in the style settings.
I really can't make it any clearer or simpler than that.
Ferryman, installing a theme is part and parcel of every software. Some use a zip file (SM), others upload it in one lump (phpBB) but if you want your own logo, etc, you still have to edit the paths on those or upload an image in the right section.
Styling and handling styles at the basic level is far easier in XF than in vB. You could simply use the color pallet and just use the original style with color changes. But you still have to upload your own logo.
I'm sorry you find this difficult. I hope you find someone to help.