Follow these steps to upload your theme/template in OpenCart:
STEP 1: Export your theme as a zip file with a File name at any desired location.
STEP 2: Log in to your administrator dashboard.
STEP 3: From the left sidebar of dashboard, navigate to Extensions –> Extension Installer. Now, click Upload.
STEP 4: Browse your theme and press “Continue” after selecting the theme. A success confirmation message will be displayed after the successful installation of the theme.
STEP 5: From Left Sidebar menu, Navigate to Extensions–> Extensions–> Extension Type. Here in Choose the extension type, select Themes(1).
STEP 6: When you select Themes(1), a Themes Bar will display on the screen as shown below. Go to Your store and click the Edit Button in the extreme right of it.
STEP 7: Now a Default Store Theme screen will open as shown below, Here in Theme Directory, browse your theme and Status is by default Enabled .Save your settings by clicking Save Button from the Top Right corner of the screen.
STEP 8: Now in Extensions navigate to Extensions –> Modifications. After refreshing your screen, you can see your TemplateToaster Theme here.
STEP 9: You are done and may visit the site to see how it looks on browser just by clicking home.