While I know nothing about SSL or installing SSL Certificates, I’m sure one of the many results Google will give me for CentOS, SSL certs and Apache would help.
However, the certificate files which have been provided for this project are a .pfx file, .cer (the certificate) file and a .txt (apparently a certificate request) file, none of which are mentioned in the articles I’m finding.. they all talk of .crt and .key files.
Is there a particular way I should be converting these files, presumably via openssl, into something I can use in Apache?
.pfxfiles tend to be PKCS#12 files (which will contain the private key, the certificate and possibly the issuer certificate chain). They’re sometimes called.p12. OpenSSL can extract private key and certificate from PKCS#12 files (via itsopenssl pkcs12command), you should be able to find documentation to do this, via Google or other questions on SO.