lupdate qmpdclient.pro -ts xx_YY.tswhere
xx is your language code, and YY is your country code (e.g. nn_NO.ts).
lupdate qmpdclient.pro -ts /path/to/old/translations/nn_NO.tsNow, open the .ts file in Qt Linguist and translate the strings (click here for help).
Once you are done, create a release file (File > Release), and send both the resulting .qm and the .ts files (e.g. nn_NO.ts and nn_NO.qm) to havtknut@tihlde.org and I'll add it to the webpage.