In order to install the extension, you need to have package file which can have such name: adk_mail-OC23-2.3.62.ocmod.zip.
adk_name – package name,
OC23 – OpenCart version code. It can be OC20 for OpenCart 126.96.36.199 – 188.8.131.52 inclusive and OC23 for OpenCart 2.3+.
2.3.62 – version of the package.
ocmod.zip – package suffix in order for OpenCart Extension Installer can recognize it.
Since the package size is more than the average, Your system may forbid it to upload. So if You’ll get the error like that in figure 1 you need to set PHP configurations ‘upload_max_filesize’ and ‘post_max_size’ to 15MB each. If Your store is on shared hosting – use cPanel or refer hosting support, in case of VPS/Dedicated server – modify the configuration file the PHP server reads and optionally restart HTTP server.
Figure 1. Package installation error
If for some reason the above approach doesn’t fit You – You can upload files using your favorite FTP client.
If You are updating the extension and Your OpenCart version is lower than 3 and extension’s modifications were added to OpenCart installation via Extension Installer – You need to remove the previous OCMOD modification. To do it go to ‘Extensions > Modification’ page, check the Mail Manager modification and click button ‘Delete’ (figure 2)
Figure 2. Modification removal.
After You installed the package via Extension Installer you need to go to ‘Extensions > Modifications’ page and refresh modifications (figure 3)
Figure 3. Modifications refresh