That is the correct way to go about it.

How high a capacity is your charger ?

Do be aware that diesel cars need quite a bit of 'oomph' from the battery to get them going. A small charger might not provide enough power to do this in a few hours, and might need a day or so.

Alternatively, the battery itself might be kaput, or something else might be taking power off the battery (so as you charge it, something else is instantly draining it).

If the car is driveable take it to your local car spares shop or halfords, most places that sell batterys will test your battery for Free.

If the battery is original being only 2 years old it should still give you several years good service unless you are only driving short distances which may not replace the charge used to start the car

If its not driveable because it will not start I would find my radio code, then after checking the owners manual for any guidance relating to charging or changing the battery I would disconnect the battery and carefully look for the earth strap ( leading from the negative terminal of battery)

Clean the battery terminals with fine wire wool or a small wire brush and do the same to the earth strap.

Using a suitable battery charger charge the battery for several hours, ensure all terminals are clean then re connected and try to start it.

disconnect the negative connection before the positive, or you may cause damage to the vehicle’s electrical system. reconnect positive cable first