Go to User Groups->iCMSUser in admin panel of CMS Made Simple in admin panel and open "Admin Preferences". Select in options tab SOAP integration method of your server. Generally you have 2 possibilities:
The first option requires that PHP SOAP extension is available on your server. If the option is not available, then you do not have extension installed. You can check it by viewing phpinfo() options. If the extension is not activated you can use nuSOAP Module as the second option. Please be aware that native PHP Extention is more powerful. nuSOAP Module is suitable for small projects with only few users because it will slow down your server. You cannot not leave this field empty. If you choose nuSOAP Module verify that the module is installed and activated in your CMSMS installation (normally by default it is so).
Attention!!! You MUST protect directory /modules/iCMSUser/services with .htaccess password before you start integrating your applications. Otherwise your server will be open for remote access and everybody will be able to create a client and connect to your server gaining access to all your applications. So if you do not protect the directory your site will be extremely vulnerable and your complete data can be damaged. There is no other way to do it, so DO PROTECT before next step. Once done you have to provide htaccess user and password into administration panel of iCMSMS module (1):

Secondly (2), choose secret hash string to protect cookie for your project. Do not use the default one, since it is public! Change it now. This string will be used to decode and encode cookie and must be long and complex. You do not need to keep it in mind :)
Cookie domain is not used in the current version. I had a lot difficulties with cookie domain serving different browsers. The actual solution does not need the field at all. But I am not sure if I need it later on again therefore still there. Just leave empty.
You are ready to connect! The first integration will be made for FrontEndUsers module of CMS Made Simple.