Hi Harshitha,
If your scenario is logging into an application using different credentials, could you please advise why you are looking to execute it sequentially ?
In terms of storing your credentials, you can create one data template and inside this template, you can create different datasets for each user. The following articles will demonstrate that:
https://subject7.atlassian.net/wiki/spaces/SD/pages/37322848/Create+a+Data+Template
https://subject7.atlassian.net/wiki/spaces/SD/pages/37781533/Add+a+DataSet+to+a+Data+Template
Once you have created the data template and added datasets to it, you can inject them in your test case by using Inject icon in steps with Fill command for the username and password. When your test case is ready, you can create an execution set from Library > Execution Sets, select the test case on the 2nd tab and select the datasets you would like to run. Please refer to the guide below (Section: Test Case and Data Set Selection):
https://subject7.atlassian.net/wiki/spaces/SD/pages/40468511/Create+an+Execution+Set
Regards,
Subject7 Team