There are various ways to import translations from a file.

In the control center​

In the menu of the "Start to translate" card, you can find an "IMPORT FILE" entry.

In the global view​

You will find the IMP (import) button next to the EXP (export) button.

In the focus view​

Also in the focus view you will find the IMP (import) button next to the EXP (export) button. Useful when importing additional translations in an existing namespace.