Fetch missing dependencies and install the package:

$ sudo dpkg -i subgit_3.2.4_all.deb
$ sudo apt-get install -f

To verify SubGit installation close Terminal application, then open it again and run subgit --version command:

$ subgit --version
SubGit version 3.2.6 ('Bobique') build #3714
  (c) TMate Software 2012-2017 (http://subgit.com/)

It should show correct SubGit version.

If it does not – verify all the steps above are followed precisely. If it doesn't work anyway – don't hesitate to contact us at support@subgit.com