General aviation pilot reported they did not follow the assigned obstacle departure procedure which resulted in ATC providing vectors to provide obstacle clearance.

Narrative

I filed an IFR flight from ZZZ to ZZZ1. Because I'd only flown one other private airplane IFR flight; I needed the practice. I filed; then later telephoned to receive Clearance from Clearance Delivery. They did mention the 'obstacle clearance departure' or something similar; which I acknowledged and understood to mean a particular departure procedure that must be on a departure page in Foreflight. Upon searching foreflight; I did not find such a departure; so I incorrectly assumed they meant; 'avoid obstacles.' This did not concern me because it was a completely clear day.Because there is no useful radio frequency on the ground in ZZZ and there was a very short time window; I knew I would have to receive departure clearance over my cell phone while taxiing out. So; I began our taxi to runway XX. With calm winds; this southerly departure made the most sense.After an avionics issue which interrupted and delayed our taxi several minutes; I removed my headset and made the phone call with our quite noisy engine running. I heard the clearance with only 3 minutes to get airborne. Just then; 2 aircraft reported on final to land; pushing us right up to the very edge of our time slot. I was rushed.Minutes after departure; I contacted departure on the prescribed frequency and I was surprised to hear that I was 'not on the prescribed course;' and told to climb to altitude ASAP. (I think it was to 4;000') I was soon cleared on course; but told to call for a 'possible deviation.'I spoke to someone; who patiently explained what had happened. He told me of the particular route I should have flown and why. (min safe and vectoring altitude is 4;000' to the south of ZZZ; but much lower to the north; so ATC cannot direct us below those altitudes) I still could not find a page in my Foreflight pertaining to this special procedure from ZZZ; but did eventually find a small note under 'Takeoff Minimums' tab hidden amongst several pages of airports. I admit i did not initially look under this heading because 'takeoff minimums' I associate with visibility; not procedures. Not until you open this tabbed section does it also state;'(Obstacle) departure procedures; and diverse vector area (radar vectors)'While I do admit to the mistake; I believe that more pilots will make this mistake as long as this section of our charts is labeled only as 'takeoff Minimums.' If either (1) this special procedure were added as a separate Departure page; OR (2) this tab labeled 'takeoff minimums' were re-labled with its full title it would be much better. I apologize for the mistake; and am sorry for any consternation it gave the controllers.