it depends on your environment and LibreCAD version. Tell me your operating system and which LibreCAD version you use. Have you used a binary installer package to install LibreCAD or did you build from source?
Generally, you can't use the *.ts files from pootle directly. The ts files have to be transferred into qm files using the Qt tool lrelease. This is done automatically when building from source. Then the qm files have to be stored in an appropriate place which depends on the operating system.
We sync the pootle server with the source code repository on github from time to time, on request or before releasing new stable versions. This is how the translations find their way into the official installer packages.
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