Presumably you received this pre-translated file from someone else?  In this case you have two options at least:

1. open your existent translation memory in the translation memories view and import the SDLXLIFF (pre-translated bilingual file), or
2. open the SDXLIFF in the Studio editor as a translation project and add your existent translation memory to the project.  Then run a batch task from the Batch Tasks menu in the ribbon to update your translation memory.

Paul,

thank you for your suggestions.

If I opt for the first option, could you please let me know whether this procedure is all right: 

in the Home tab of the TM view I choose the Import tab and do import of the sdlxliff files of which TM I want to add to my existent TM. Is that correct?

Thank you,

Milada

Unknown said:

in the Home tab of the TM view I choose the Import tab and do import of the sdlxliff files of which TM I want to add to my existent TM. Is that correct?

I think you have the right idea... so just checking.  You are going to be importing the SDLXLIFF files you select into your existent.  In here:

Yes, exactly like this Paul,

Milada

Perfect then...

Thank you for your help today

Milada