can i use my personal email address for schedule tasks since i do not have mail server?
In order for Open-AudIT to send email, it needs an email server to interact with. This is a requirement.
I am using Gmail, so how to setup mail server for it and because of that i cant schedule any tasks such as detect and report for when there is someone install a new app on the network's machine.
please check the gmail documentation for these settings; most likely you'll find https://support.google.com/a/answer/176600?hl=en and https://support.google.com/mail/answer/7104828?hl=en useful.
to expand on chris' answer, if you want to use your personal email address then you'll have to use your email provider's mail server.