First, you need to educate yourself about ISO 13485, what kind of standard it is, what are the specific requirements in it. If any requirements in Clauses 6, 7, and 8 are not applicable due to the nature of the medical device, those requirements can be excluded.
For example, if your medical device is not sterile, then requirements 7.5.5 Particular requirements for sterile medical devices and 7.5.7 Particular requirements for validation of processes for sterilization and sterile barrier systems are not applicable for you.
If your medical device is software, then several more requirements are not applicable: 6.4.2 Contamination control; 7.5.2 Cleanliness of product, 22.214.171.124 Particular requirements for implantable medical devices.
Then you need to be sure that you have a medical device. ISO 13485:2016 is applicable for manufacturing medical devices. Definition what is a medical device you can find on the following link:
The next important step is to define your processes and to make all necessary documentation procedures and records. In that, very helpful can be a documentation toolkit. It is a set of pre-written templates, easy-to-use, fully compliant policies, procedures, and records.