Offical documentation - https://www.soapui.org/getting-started/installing-soapui/installing-on-linux-or-unix/
Snipet
wget https://dl.eviware.com/soapuios/5.7.1/SoapUI-x64-5.7.1.sh
sh SoapUI-x64-5.7.1.sh
After that just click Next to continue.