In case you have sufficient privileges and don't fancy the latest release, the by far easiest option is the Ubuntu/Debian package manager apt.

sudo apt install ncbi-blast+

This answer should help you.

1.Retrieve blast executables (if not already done) in the terminal:

1.1 Download the executables with the command:

wget ftp://ftp.ncbi.nlm.nih.gov/blast/executables/blast+/LATEST/ncbi-blast-2.10.0+-x64-linux.tar.gz

1.2 Decompress the archive and rename it:

tar zxvf ncbi-blast-2.10.0+-x64-linux.tar.gz
mv ncbi-blast-2.10.0+ blast
rm ncbi-blast-2.10.0+-x64-linux.tar.gz

1.3 Add a folder for blast databases

cd blast
mkdir db
cd...

1.4 you become administrator (you enter your password):

sudo su

1.5 You place the executables in /usr/share to make them usable by everyone:

mv blast /usr/share.
chmod a+w+r /usr/share/blast/db
export PATH="$PATH:/usr/share/blast/bin"
export BLASTDB="/usr/share/blast/db/"
exit

You will need to put the two export lines in files likes ~/.bash_profile or ~/.bashrc for executables o be available across all sessions.

2.Retrieves the databases (if needed for example with SwissProt DB, needs admin rights)

cd /usr/share/blast/db
cp ../bin/update_blastdb.pl .
perl update_blastdb.pl swissprot
tar zxvf swissprot.tar.gz
rm swissprot.tar.gz

Done :)