Req: I have a command button on VF page. 

When i click on it then a popup window needs to open (That can be achievable). When we add to some values those need to get saved into custom settings and those need to be available in a multi-select picklist on same page.

1. Need to save into custom settings from visualforce page.
2. Those values needs to get refresh from  custom settings to that mulitselect picklist field on same VF page.

Any Suggestions or any sample codes regarding above two points please provide me.

    /***************VF page******************************/
    <apex:page controller="Sample_Groups" sidebar="false" >
    <apex:form >
        <apex:pageblock >
            <apex:pageblockTable value="{!Groups}" var="c">
                <apex:column value="{!c.Name}"/>       
             </apex:pageblockTable>
        </apex:pageblock>
    </apex:form>
    </apex:page>

 
    /*********************** Controller********************************/
    public with sharing class Sample_Groups{
    
        public List<Group_Details__c> Groups{get;set;}
      
        public InvestorGroups()
        {
            Map<String,Group_Details__c> allGroups = Investor_Details__c.getAll();
            Groups = allGroups.values();
        } 
      
    }