Many distributions already provide fail2ban packages, so better you'd install this built from your maintainers version of fail2ban, especially if you are not familiar with linux.

You don't need install fail2ban for the test attempts or to try some new functionality, so firstly read How to test newer fail2ban version resp. use fail2ban standalone instance.

If you already have fail2ban installed from your distribution:

• backup your current configuration /etc/fail2ban and run-time database /var/lib/fail2ban/fail2ban.sqlite3
• you can also store the dump of your current configuration to be able to compare it later:
  fail2ban-client -d > /tmp/f2b-dump-of-prev-version.txt
• if your fail2ban version departs significantly or you decided install from source, stop and uninstall obsolete version of fail2ban

If you have debian-based distribution, you could try to install debian packages from newest releases. This upstream package is very similar the package maintaining for the latest debian stable version, but can also work for the most other debian-based distributions.

cd /tmp/
# 1) download deb package and signature:
wget -O fail2ban.deb https://github.com/fail2ban/fail2ban/releases/download/1.1.0/fail2ban_1.1.0-1.upstream1_all.deb
wget -O fail2ban.deb.asc https://github.com/fail2ban/fail2ban/releases/download/1.1.0/fail2ban_1.1.0-1.upstream1_all.deb.asc

# 2) check signature (if you want to be sure file is unmodified):
gpg --verify fail2ban.deb.asc fail2ban.deb

# 3) view details of the package:
dpkg -I fail2ban.deb

# 4) to ensure the upgrade run gentler (protocol of previous version may be incompatible), stop fail2ban before install:
# using service:
sudo service fail2ban stop
# using client:
sudo fail2ban-client stop

# 5a) either install package using dpkg (standalone package, don't regard dependencies):
sudo dpkg -i fail2ban.deb
# if the package introduces some "broken" dependencies (I don't think so in case of fail2ban which has few dependencies),
# to fix the unmet dependency issue, run this:
sudo apt -f install

# 5b) alternatively install package using gdebi (that will take care of installation of dependencies):
sudo gdebi fail2ban.deb
# if you want to check anyway whether there are some broken packages and fix them automatically, you can run:
sudo apt -f install

Note: although in opposite to installation from source, it would also install service units, man-files, bash-completion etc, the package configuration can also deviate from configuration provided by maintainers of your distribution. Additionally note that the upstream packages are provided without the test-suite (fail2ban-testcases, fail2ban.test python module).

Manual install/upgrade is very similar to aforementioned testing of standalone instance, just you have to do more steps to install it, like copy and enable service units, copy man-files etc pp.

sudo cp ./build/fail2ban.service /etc/systemd/system/fail2ban.service
sudo systemctl enable fail2ban

Now we have to configure fail2ban (also see Proper fail2ban configuration):

• copy your .local files from backup to /etc/fail2ban (or create new jail.local and set-up jails you need to enable).
• take a look in your backup copy of /etc/fail2ban/jail.conf for includes made for your distribution:

[INCLUDES]
before = paths-debian.conf

• copy this file and set the same line in new jail.conf or jail.local in /etc/fail2ban.
• test it
  sudo fail2ban-client --test

Now you can start fail2ban via service:

sudo service fail2ban start