When adding keywords to "Keyword Picker" attributes using the '[edit keywords]' under Admin > Attributes > Manage attributes, you can import keywords from an external file.

After clicking on the 'Import keywords from a file' link follow the instructions on the page and use the sample import file as a starting point for your import.

Alternatively, if you regularly need to import a keywords file you can use the "Keyword Import URL" property when editing the Keyword Picker attribute.
The system will then import keywords from the remote file following a polling interval specified by the following setting in the ApplicationSettings.properties file:

keyword-import-poll-period-minutes=60 

NB: If you are importing hierarchical keywords into a Keyword Picker attribute:

If you are importing a hierarchical keyword taxonomy (instead of using the simple Name/Synonym setup above) Asset Bank requires a delimiter to be set between the Parent and Child keywords for the Keyword Picker attribute based on a setting in your ApplicationSettings.properties file:

category-ancestor-delimiter=/

The default delimiter is a forward slash '/' but it is worth checking what you have set in your settings file before importing keywords from a file, as some custom configurations use a pipe '|' and some also use a forward slash '/'.

Here is an example of a hierarchical keyword string using a forward slash:
Nature & environment/Bodies of water/Oceans/Arctic Ocean