Telemetry scripts are organised on the radio in the /SCRIPTS/'Modelname' folder (OpenTX 2.0) or the /SCRIPTS/TELEMETRY folder. The name of the script must be telem1.lua-telem7.lua for OpenTX 2.0, or any name.lua less then 6 characters for newer OpenTX versions. On versions higher than OpenTX 2.0, the script has to be selected as output page in the telemetry setup in the radio lenu.
To start a telemetry script, you need to long press PAGE.
Most well-written telemetry scripts can run as a One-time script as well. Just use the SDcard browser to locate the file, and long press ENTER to execute it.