OpenSSL help in Swift

Hi! I’m new to the forum and a fairly new iOS developer. I’m new to this community too!!
I’m building an iOS app that communicates to the Argentinian TAX Department (US IRS, ARG AFIP), you communicate to its API with encrypted soap xml commands which are encrypted using openssl.
I’m a beginner developer so I don’t understand a lot of security (although it does not seems hard) or scrips (don’t know what they are). I can run openssl in the terminal and get the result I want. To do that I have to run this command

openssl smime -sign -signer certificate.cer -inkey Mikey -out ticket.xml.cms -in testticket.xml -outform PEM -nodetach

I really don’t understand when people tell me about a shell script to build openssl for iOS or you can try to write a wrapper for an openssl version or compile your own framework
Could anyone tell me where I can find a good reference to this subject. Or an example to this.
Can you give me any advice?

Thanks a lot for your time