You can import
Ribbon Select the Resources ribbon. In the TMX section select Import TMX.
Translate Toolbar Click .
To open the Translate toolbar from the menu view, you can select View>Toolbars>Translate.
The Import TMX File dialog opens.
(Optional) If you want to be informed of matching segments, click Check TMX for repeated segments.
If this option is selected, you will be informed if alternative or duplicate segments are found in your TM. Duplicate segments are not reimported.
example
Let's say you have the text "This is a car." In your TM database, you already have this translated, using the word "coche" for "car." In the TMX file you are importing, the translation is much the same, except the word "carro" is used. Therefore, Lingo informs you that an alternative translation has been found.
On the other hand, if the translation in the TMX file also uses the word "coche" in the translation, Lingo informs you that a duplicate translation has been found.
If you do not select the option to check for repeated segments, the import process is faster. However, you are not informed of duplicate or alternate translations. Whether you select the option or not, the translations in the TMX file are added to the TM database.