Since psndlnet implies a network source, ensure you can reach the server:
conda install package_name
to mount PKG files from non-FAT32 drives and then install them through the standard Package Manager on the PS3 XMB. Remote Package Installer
For a smoother installation experience, it is highly recommended to use to move large PKG files directly from your PC to the dev_hdd0/packages folder on the PS3, bypassing USB speed limitations.
Understanding PSNDL.net: How to Find and Install PlayStation Packages
pip install --index-url https://psndlnet.example.com/simple/ your-package-name
To install custom or homebrew PKG files, your PS3 must be jailbroken (CFW or HEN).