You can only add user dictionaries with the extension *.lsd created in ABBYY Lingvo x3.
To add user dictionaries, you first need to convert them to the Lingvo x3 format using DSL Compiler, which shipped together with ABBYY Lingvo X3 (to start DSL Compiler, select Start > All Programs > ABBYY Lingvo x3 > DSL Compiler x3). If you do not have a copy of ABBYY Lingvo x3 installed on your computer, you can have your user dictionaries converted by sending them to ABBYY technical support team.
You can add only user dictionaries for the languages supported by ABBYY Lingvo for Mac:
To add an *.lsd, follow these steps:
1. Open the Go > Libraries > Containers > com.abbyy.lingvo > Data > Library > Application Support > ABBYY > Lingvo > User dictionaries folder if you have purchase ABBYY Lingvo for AppStore.
Open the Go > Library > Application Support > ABBYY > Lingvo > User dictionaries folder if you have ABBYY Lingvo not for AppStore. In this folder, select the folder that bears the name of the source language (i.e. the language from which to translate), in that folder open the folder bearing the name of the target language (i.e. the language into which to translate), and copy the dictionary to that folder.
For example, if you are adding a French-Russian dictionary (Fr-Ru), the path will be as follows: Go > Libraries > Containers > com.abbyy.lingvo > Data > Library > Application Support > ABBYY > Lingvo > User dictionaries > fr > ru (or Go > Library > Application Support > ABBYY > Lingvo > User dictionaries > fr > ru).
2. Quit ABBYY Lingvo (ABBYY Lingvo > Quit ABBYY Lingvo).
3. Open the program to make sure that the dictionary has been added.
Note: to navigate to the Library folder, please click on the 'Go' menu in Finder, hold the Alt button on your keyboard - the needed item appears in the drop-down list.