This quick blog was requested by someone on IRC and it details how to set up an outproxy on i2p.
If this is too quick a guide or you feel like you don't know what you're doing then I'd suggest against running an outproxy.
The setup process goes as follows:
install i2pd and tinyproxy
edit tinyproxy.conf to have sane defaults
have tinyproxy deny access to loopback
create an i2p server tunnel pointing to 127.0.0.1:8888
publish destination of outproxy
User tinyproxy Group tinyproxy Port 8888 Listen 127.0.0.1 Timeout 600 DefaultErrorFile "/usr/share/tinyproxy/default.html" Logfile "/dev/null" LogLevel Warning PidFile "/run/tinyproxy/tinyproxy.pid" MinSpareServers 5 MaxSpareServers 20 StartServers 10 MaxRequestsPerChild 0 Allow 127.0.0.1/8 ViaProxyName "tinyproxy" Filter "/etc/tinyproxy/filter" FilterExtended On ConnectPort 443