Not enough information to help you.

Thunar is a file manager. It has nothing whatsoever to do with installing a printer.

What distro/version of Linux are you running and what is the make/model of the printer?

Is CUPS installed and enabled?

Is the printer connected via USB, is it directly on the network, or is it networked from another computer?

Inquiring minds want to know.

Welcome to the forum! While we are always happy to help, we are not mind readers. But the following are good places to start.

If your printer is HP:
> switch it on and connect it to the computer
> look in the menu for a terminal program, run it
> enter the command "sudo hp-setup" and hope for the best!

If it's a Samsung, go to their site, download the Linux Unified Driver, and follow the instructions.

If it's something else:
> start your browser
> enter the address http://127.0.0.1:631/
> read the on-line help if necessary
> go to Administration - Install printer

I don't think that's really needed. I have two HP printers and was able to set them up with the CUPS web interface just fine, using the last method you suggested:

Unless there some advantage to using hp-setup over the standard web interface that I'm just not aware of?

HPLIP has many facilities available, as you can see from their web-site. Are those facilities set up if you don't install via HPLIP? I'm not sure, but if HP provide special software and the distros include it, it's probably a good idea to use it. It's certainly quicker, as it identifies the printer for you, so there's no typing or selection to do: keep life simple! What I am sure about is that if you use hp-setup for a multifunction device, then both printing and scanning will be configured.

Sorry about my post guys. Here is the additional information. Plus i dont know what CUPS means. How can i check if its enabled? Sorry guys im just a newbie. Sorry again.

.it is a canon printer usb
.thunar is installed in a medical equipment built-in computer.
.the said equipment has 4 usb 2.0 ports.

I hope i give the right information on you guys. Thanks again

CUPS is the Common Unix Print Server. The Arch Wiki has a good article about it: https://wiki.archlinux.org/index.php/CUPS

It really is necessary to know, not just the make, but also the model of the printer and what is running on that medical device.

It's also important to know what flavor of Linux is on it, as different branches of Linux handle installing and managing software packages differently. Possibly the manual for the device will contain information about installing a printer.

Note that it is entirely possible that the Linux on the device is some customized embedded system and not a regular Linux distro. In that case, the device manufacturer would be your best source of support.

How do you access the software on the device? Is it some sort of graphical interface or command line? If you have access to a terminal, try one of these commands:

Most Linux distros have a file in the /etc directory named something-issue--something or something-release-something. If there is such a file, one of those commands will output its contents to the terminal. Here's an example from the computer I'm using at this moment:

thunar is just the file manager and not responsible for the printer.
you really need to access all of the operating system to fix this.
the terminal would be a good start.