I am not clear precisely what you are asking, but I think you mean that you wish to suggest a reviewer for a manuscript you submitted? If so then just write to the editor who is handling your manuscript with the suggested name. They may or may not use the reviewer you suggest, that decision is up to the handling editor.

Dear Maha Maki In addition to what is indicated by Michael J. Benedik you can come up with suggestions, you can do this by:

-Using names you know in your field of expertise

-Using names of those who published relevant papers in your field

-Using names of the publications you cited

Nowadays all the relevant contact info can be found in their publications.

Best regards.

PS. You do not have to know these people personally, the journal just want to increase their network of potential peer-reviewers with people you estimate to be able to review your manuscript.