References and descriptions can be set to post to the General Ledger in Accounts Receivable or Cash Receipts, Setup.  Click on the Detail Tab and there is a blank column labeled "Options" next to the journals listed on the top of the form under Journal Settings.  Click in the blank field and an ellipse will appear. Click the ellipse, and items can be selected from the dropdown next to Desc1, Ref1, Ref2, and Ref3. Data items are also listed but those are not functional at this time.

You must also have the Detail checkbox selected under the Posting Settings for the types of transaction you wish to post the items above.

For any changes made, the detail posting is not retroactive, but can be tested by posting an entry and adjusted as needed.

Note: If you are using AR7 or CR7 and not also using Classic AR or Classic CR the journals can be set up with different options. This means if you want different references to post to GL on a Cash Receipt than you are posting on an invoice you can do that.  However, if you also use Classic AR or CR and are using the same journals, then all journals used within the module must be identical.

Modules that were developed originally in Classic, such as AP, AR and Payroll, all have restrictions that the journals used within a module must all have the same posting settings.
This is not true of AR7 and CR7.  If you change a posting setting that affects Classic AR or CR, when posting is accessed in those modules, an error of "Journal control Data Item conflict" will be received, indicating all AR journals must be set up with the same settings.

If both Classic and gui are being used at the same time, an option is to use different journals to post in both modules.  For example, instead of using CREC to post receipts in both modules, you could use CREC for Classic and set up a new journal, such as CREC7 to use in AR7.  That allows the posting of different references, as allowed, in AR7, and also will segregate for auditing purposes which details came from Classic vs gui.