If you want to automatically log your members into the site immediately after they complete the registration, then you can enable the Enable Auto Login After Registration feature. This is an optional feature of the plugin.
Note: When you enable this feature, it will invalidate any after registration redirect that you may have setup.
This is because (when this feature is enabled) the member will always get logged into the site immediately after the registration and that will trigger the after login redirection. So you can use the after login redirection feature to configure where the user goes to after the auto login.
Do the following to configure auto login after registration:
Step 1) Go to the Advanced Settings interface of the plugin:
Simple Membership -> Settings -> Advanced Settings
Step 2) Check the Enable Auto Login After Registration field.
Step 3) Save the settings.
Now, when the members complete the registration by submitting the registration form, they will get logged into the site automatically then the after login redirection will take place (if you have configured after login redirection).