So I have an object called Purchase Requisition that has a button that leads the user to a pop up visualforce page where they select a Warehouse from a picklist which is another custom object. The picklist is generated by all of the records in the Warehouse object. I had to do this because users don't have access to Warehouse due to the cost of licensing. I want whatever their selection is on that window and then hit save, to then save the warehouse name as a text field on the purchase requisition records that they started with. I'm not really sure how to go about that. Here is the VF page and controller that I have built so far. Any help is appreciated!
 

public class selectWarehouse {
    private final Purchase_Requisition__c pr;
    
    public selectWarehouse(ApexPages.StandardController stdController) {
        this.pr = (Purchase_Requisition__c)stdController.getRecord();
    }
    public string selectedWarehouse{get;set;}
    
    public list<SelectOption> getWarehousenames() {
        List<SelectOption> options = new List<SelectOption>();
        for (Warehouse__c w : [select name from Warehouse__c order by name desc limit 100])
        {
            options.add(new SelectOption(w.name, w.name));
        }
        return options;
    }
}

 

<apex:page lightningStylesheets="true" standardController="Purchase_Requisition__c" extensions="selectWarehouse" showHeader="false">
    <apex:form >
        <apex:pageBlock title="Select A Warehouse">
            <apex:outputLabel value="Warehouse "/>
            <apex:selectList size="1">
                <apex:selectOptions value="{!Warehousenames}">
                </apex:selectOptions>
            </apex:selectList>
            <apex:pageBlockButtons >
                <apex:commandButton action="{!save}" value="Save"/>
            </apex:pageBlockButtons>
        </apex:pageBlock>
    </apex:form>
</apex:page