Step 1:

Navigate to Live Helpdesk > Administrator > Knowledgebase > Enable (Integrations/Knowledgebase) > Select Live Knowledgebase module from the dropdown

Step 2:

Navigate to Live Forms > Manage > options > Actions > On Form Submission > Add Action > HelpDesk > Create Ticket

Step 3:

Map require fields and specify Live Knowlegebase Token > Save

Step 4:

Add HTML module on the page with the Live Knowledgebase Token specified

Step 5:

Now you can see Related Solutions while specifying any keywords in Subject field