To use repos directly in your system first create repository file with repo data. Remember to change baseurl to your system
If you are using yum do this
# vim /etc/yum.repos.d/kurwinet.repo
[kurwinet]
name = Kurwinet repository
baseurl = https://yum.kurwinet.pl/rhel-7
enabled = 1
gpgcheck = 1
gpgkey = https://yum.kurwinet.pl/bofc-signing.pub.key
If you are using zypper instead of yum, you can add repository this way.
zypper ar -f https://yum.kurwinet.pl/opensuse-15/ kurwinet.pl
Now just import key and you are good to go
# rpm --import https://yum.kurwinet.pl/bofc-signing.pub.key