It is also possible to manually install the NCBI BLAST+ binary files. You can download the latest version of Blast+ from here:
https://ftp.ncbi.nlm.nih.gov/blast/executables/blast+/LATEST/
Note that NCBI discontinued Blast+ support for 32-bit windows in 2015. If you have a 32-bit Windows system then you will need to install the last 32-bit compatible release of Blast+ from:
https://ftp.ncbi.nlm.nih.gov/blast/executables/blast+/2.2.31-last-win32-release/
Choose the appropriate installer for your operating system, download and extract it and install Blast+ an appropriate location on your computer.
You will then need to let Geneious know the location of the Blast+ installation. To do this, go to menu Tools → Add/Remove Databases → Set Up BLAST Services and set Service: to Custom BLAST. Enter your data location or click Browse to point Geneious to the location of the Blast+ folder. Uncheck the option to Let Geneious do the setup and click OK. Geneious will now use your manually installed Blast+ executables.