if you want to do it through Apex,

below example should help you. 

 //Lead Conversion

        // creating a sample lead for conversion
        Lead ld1 = new Lead();
        ld1.lastName = 'test'; // these 2 are the required fields in my Org, as per your Org required fields 
        ld1.Company = 'test';    //  assign values to each of the required fields
        insert ld1;

        // converting the created lead
        Database.LeadConvert lc = new database.LeadConvert();
        lc.setLeadId(ld1.id);
        //lc.setAccountId(acc2.Id); // you can set the Account Id to which you want the lead to be converted, if not specified, it creates a new account.
        //lc.setContactId(con3.id);  // you can set the Contact Id to which you want the lead to be converted, if not specified, it creates a new Contact.
        //lc.setDoNotCreateOpportunity(true); // this will not create a new opportunity on lead conversion
        
        LeadStatus convertStatus = [Select Id, MasterLabel from LeadStatus where IsConverted=true limit 1];
        lc.setConvertedStatus(convertStatus.MasterLabel);
        Database.LeadConvertResult lcr = Database.convertLead(lc);
        System.assert(lcr.isSuccess());
        system.debug('-----------'+lcr.getContactId()); // will return you the converted Contact Id
        system.debug('-----------'+lcr.getAccountId()); // will return you the converted Account Id

Let me know if this helps :)