As we already know, opencart is a popular e-commerce CMS (Content Management System), open-source, PHP based, that is running with MVC (Model-View-Controller) architectural pattern.
Download and Install XAMPP
In fact installing OpenCart on your computer won't take less than 5 minutes. You need to download latest or any version of XAMPP compatible with your device from here or Apache Friends. After the successful installation run XAMPP server, start apache and MySQL modules from action's column. Make sure both are running over checking status box, if it fails to start you should reinstall XAMPP server. Note that MySQL does not work properly if already installed using other applications. Once finished above configuration open any browser and type localhost and hit enter. You might see XAMMP's welcome screen. Yep done, now we just created a context for running any websites without obstruction.
Installing OpenCart on Local Environment
Moreover one step is queuing, download fresh copy of OpenCart from its official website. Extract uploads folder from downloaded zip file and copy them into htdocs directory. Usually it stored on c:/xampp if you didn't changed installation path. It can also able to find from Explorer button on XAMPP control panel. Rename unzipped uploads directory to any name you like eg. opencart. I've named it as opencart. Create a new database to store back-end database for your e-commerce site by using phpMyadmin,to do so, type localhost/phpmyadmin in browser URL bar and tap enter. I've named it as opencart. Open opencart folder from htdocs directory, change config-dist.php to config.php and in admin directory as well. Now go to your online shop via localhost/opencart URL. You should complete four out of four steps to finish to opencart installation. On configuration setup change the credentials similar to below image if you don't know what you're doing.
Tweaking some mandatory files similar to what i have now will overcome failure rate. Depending on my assumption you made the same names for all kinds of folders and files else change them to corresponding name you've created early.
Eventually go to localhost/opencart to get access to your local site , login to backend via localhost/opencart/admin