Here's the general procedure. I don't know if/how much of this you might have done already.
Log in to your Hero Lab Online/Realm Works account:- Go to https://www.lonewolfdevel.com/ .
- If you don't have an account there, make one.
- Log in.
Associate your HLC licenses with this account:- In the top bar, select your account name and then Manage Account.
- In the list of pages on the left, pick "Classic Licenses".
- Under "Associate Classic Licenses", put in a license number and the associated email address, then click "Associate License to My Account".
- If necessary, do this for each of your Classic licenses. (You should have at least 2, you may have more; I don't remember if you have to do each one or if it picks up all the linked ones for you.)
Enable PF1 in Hero Lab Online:- In the list on the left, select Store. (From the Home page, select "Shop Hero Lab".)
- Pick "Pathfinder 1st Edition" in the Hybrid (center) column.
- Here I can't tell you exactly what to pick since their store hides things, but you're looking for an "Add PF1 Classic purchases to HLO" option (~$10, IIRC). This should be an alternative to purchasing PF1 system access outright. ($25)
- If you don't already have some, you'll also have to buy HLO access time.
Once you have your previous purchases added to HLO, you can use both HLC and HLO with Pathfinder 1e. If you have more than one Game System in HLO, you can switch by selecting the Hero Lab or system logo at the top left of an HLO page and picking Select Game System.
Note that while you can upload characters to Online, you can't bring characters out of Online to use in Classic.
Hope this helps.