SecurID setup is supported only from the command line on vCenter Server version 6.0 or later. The configuration is well explained in the following blog post: https://blogs.vmware.com/vsphere/2017/07/using-vcenter-login-banner-rsa-securid-support.html.

Then the integration is quite simple on the web client authentication page:

RSA authentication manager requires that the user ID is a unique identifier that uses 1 to 255 ASCII characters. The characters ampersand (&), percent (%), higher than (>), less than (<), and single quote (`) are not allowed. Also, the RSA SecurID agent that is integrated into the PSC component of vCenter does not support PIN resets.