Hi Jeanette,
Full rubber ring sits in lip under the tap, connecting between tap and worktop, the ‘c’ style rubber and metal washer fit underneath. In that order usually. The 2 larger holes are for the flexi hoses, and the narrow hole for the threaded stem.
Remove the bolt from stem, attach stem to the tap and tighten.
Attach flexi hoses in base hand tight, also fit full rubber washer in lip underneath tap and position tap in worktop.
Offer the rubber ‘c’ washer, metal washer and bolt to the stem, and tighten by hand, and finish using a suitable box spanner.
Connect flexi hoses to hot and cold pipework.