You should press "Create pull request" , add SPARK-1731 somewhere in the name of this PR, say "Update spark_i18n_uk_UA.properties - SPARK-1731" and then press "Create pull request" again. Adding SPARK-1731 will link this PR with [SPARK-1731] Add Ukrainian translation - IgniteRealtime JIRA which i have temporarily reopened (this is good to have for a history of changes related to the ticket). After you submit PR, i will get a notification and will merge it to the main source. You will get notification about that on Github. Then Bamboo will automatically produce new installers (10-15 minutes) and you will find a new build on the nightly downloads page Ignite Realtime: Spark Nightly Builds
Keep in mind, that i'm going to merge 3-4 PRs in the near time. So the build with your changes might be with a higher number (821 or 822 probably). Well, it will be in the latest build after you get the notification
Also, since 817 build there is an issue that Spark is not able to login at all. This hopefully will be fixed soon in one of those PRs, but i can't guarantee.