I know how important it is to account for your company's assets. I'll help guide you in the right direction to record this in QuickBooks Online.
If you've bought the computer outright, it should be recorded as a fixed asset and depreciated accordingly. If you haven't already, the first step will be to set up a Fixed Asset account in your Chart of Accounts. Here's an article explaining how to do that: How do I add a fixed asset account to my chart of account?
I recommend reaching out to an accountant if you're unsure which detail type to select, and to find out if you'll need to add a depreciation sub-account. This all depends on how you're structuring your bookkeeping. If any of our accountant users here in the Community have any tips, I'm sure they'll chime in for help.
Since you've already recorded the expense through an employee reimbursement, the next step will be to create a Journal Entry, moving the money from the Reimbursement account to the Fixed Asset account. To create a Journal Entry, click the Create (+) icon > Journal Entry. Ensure you're entering the HST in the Journal Entry as well. Again, if you're unsure which account to credit, and which account to debit, please consult an accountant.
Once the journal entry has been recorded, you'll see the expense with HST added to the Fixed Asset account.
I'm here if you have any questions or need clarification on the steps.
Have a great day!