Say, you want the class to run every 1 hour, or every 30 mins, then you cannot do it using declarative way. To do this, we can use system.schedule method and call the scheduler class. System.schedule takes 3 parameters as below :

system.schedule('jobname',timeperiod,scheduler class name)

jobname: you can give any name to your job
timeperiod: specify the time frequency with which the job should run
scheduler class name: scheduler class that calls your batch apex class.

 timeperiod should be specified in below format:
Seconds Minutes Hours Day_of_month Month Day_of_week optional_year

For example, to run every 5 mins the expression would be : 0 5 * * * ?

here '*' means every time against the specified parameter, every hour, every day of month, every day of week and '?' means no specific value. Thus, this expression means every 5 minutes. So, the system.schedule('testname',0 35 * * * ?,schedulerclass()); would call the schedulerclass every 30 minutes when the statement executes.You can visit salesforce documentation to know more on system.schedule parameters.

Lets write a simple batch apex class, its scheduler class and then, execute system.schedule method to run that batch apex every 5 minutes.

Batch Apex Class:

global class BatchApexDemo implements database.batchable<sobject>{
Public string soqlquery;
 Public void setQry(string soqlquery){
    this.soqlquery = 'Select name,status from account limit 1';
 }
 global database.querylocator start(database.batchableContext bc){
  return database.getquerylocator(soqlquery);
 }
 global void execute(database.batchablecontext bd, list<sobject> sc){
   System.debug('**In Execute Method**');
 }
 Public void finish(database.batchableContext bc){
  
 }
}

Scheduler class along with method that will Can scheduler class every 5 minutes:
 

global with sharing class ScheduleBatchApexDemo implements Schedulable {
global void execute(SchedulableContext sc) {
  ID BatchId = Database.executeBatch(new BatchApexDemo(), 200);
}
 
Public static void SchedulerMethod() {
  string timeinterval = '0 5 * * * ?';
  System.schedule('BatchApexDemo-Every15mins',timeinterval, new ScheduleBatchApexDemo());
  }
}

Now, we have to just execute the "SchedulerMethod" once, this will keep on calling the batch apex every 5 minutes. We can use developer console to execute this method. Just execute below statement to call the method: ScheduleBatchApexDemo.SchedulerMethod(); You can monitor the batch apex being called every 5 minutes from: set up--> monitoring jobs

Please mark this as the best answer if this helps