W/Assalam!
Taimur! You may apply for employment in two ways:
1. Where an advertisement has been given for the job
Method of applying for the job, as well as what information is to be provided with the job application, in normally provided in the advertisement. So, in this case, you should follow the procedure specified in the advertisement.
2. When you want to apply on your own (without any advertisement)
It would be better to apply with your CV, supported by photocopies of your educational degree (Matric onwards), and any experience or special skills certificates (e.g., computer , CAD, or civil engineering related software courses etc.).
As regards the cover letter, do a search on the internet. you will certainly find some good tips (may be some good book too) regarding how to write a good CV/resume, and what should be included in a cover letter.
Best of luck.
Regards.