Sure! This is actually pretty easy to do.
Please log into VRChat with your Steam/Oculus account. Open your quick menu, then select Settings. Near the bottom of that menu, you'll see a button to "Upgrade Account". Click that and follow the instructions on the screen to merge your accounts.
Please note: If you have favorite avatars or worlds on the VRChat account that you are merging your Steam/Oculus account into, the merge will ignore the favorites on the Steam/Oculus account.
In other words, it is best to merge your Steam/Oculus account into a new, blank VRChat account.