TRxDBGrid,
TFrPrintGrid,
TrfUserDataset,
TfrDBDataSet.
Where would I be able to download them? and hoe do I go about installing them to my Lazarus installation?
TRxDBGrid belongs to package RX.
I found TfrUserDataset in unit LR_DSet which belongs to LazReport (which comes with Lazarus, but is not installed by default). The other TFr* classes probably belong to LazReport as well. Since LazReport has been split into several packages you may have to install also other packages named like "lr*"
In order to install new components - and this is also how to install OnlinePackageManager - , go to "Package" > "Install/unstall packages". Find the requested package (lazreport, OnlinePackageManager) in the right list, click "Instal selection", then "Save and Rebuild IDE". Then Lazarus will recompile itself (which takes some time). At the end Lazarus restarts, and you'll find the new components in the palette, except for the OnlinePackageManager, which is in "Package" > "OnlinePackageManager".
This procedure works only for packages which are known to the IDE. The easiest way to install other packages is via the OnlinlinePackagemanager. Start it, find the package in the list (here: "Rx"), check it, click "Install" - wait. When Lazarus restarts you are ready to go.
It should not happen, but sometimes packages are faulty and crash the new Lazarus. Open the Lazarus folder, delete Lazarus.exe and rename Lazarus.old.exe back to Lazarus.exe in order to restore the last working version.